SERVER-17880 Rename OpTime to Timestamp

97 files changed, 1057 insertions, 967 deletions

diff --git a/src/mongo/db/auth/privilege_parser.h b/src/mongo/db/auth/privilege_parser.h
index 66349199492..aec390e3973 100644
--- a/src/mongo/db/auth/privilege_parser.h
+++ b/src/mongo/db/auth/privilege_parser.h
@@ -32,7 +32,6 @@
 #include <vector>
 
 #include "mongo/base/string_data.h"
-#include "mongo/bson/bson_field.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/s/bson_serializable.h"
 
diff --git a/src/mongo/db/clientcursor.h b/src/mongo/db/clientcursor.h
index 554fb0e7076..86d8bc0b7bb 100644
--- a/src/mongo/db/clientcursor.h
+++ b/src/mongo/db/clientcursor.h
@@ -136,9 +136,9 @@ namespace mongo {
         //
 
         void updateSlaveLocation(OperationContext* txn);
-        void slaveReadTill( const OpTime& t ) { _slaveReadTill = t; }
+        void slaveReadTill( const Timestamp& t ) { _slaveReadTill = t; }
         /** Just for testing. */
-        OpTime getSlaveReadTill() const { return _slaveReadTill; }
+        Timestamp getSlaveReadTill() const { return _slaveReadTill; }
 
         //
         // Query-specific functionality that may be adapted for the PlanExecutor.
@@ -250,7 +250,7 @@ namespace mongo {
         bool _isNoTimeout;
 
         // TODO: document better.
-        OpTime _slaveReadTill;
+        Timestamp _slaveReadTill;
 
         // How long has the cursor been idle?
         int _idleAgeMillis;
diff --git a/src/mongo/db/commands/fsync.cpp b/src/mongo/db/commands/fsync.cpp
index 8a2329c7f95..ac63457aa15 100644
--- a/src/mongo/db/commands/fsync.cpp
+++ b/src/mongo/db/commands/fsync.cpp
@@ -30,6 +30,7 @@
 
 #include "mongo/db/commands/fsync.h"
 
+#include <boost/thread/condition.hpp>
 #include <iostream>
 #include <sstream>
 #include <string>
diff --git a/src/mongo/db/commands/get_last_error.cpp b/src/mongo/db/commands/get_last_error.cpp
index 2a376a369a4..065fc484d58 100644
--- a/src/mongo/db/commands/get_last_error.cpp
+++ b/src/mongo/db/commands/get_last_error.cpp
@@ -130,7 +130,7 @@ namespace mongo {
             Client& c = *txn->getClient();
             if (repl::getGlobalReplicationCoordinator()->getReplicationMode() ==
                 repl::ReplicationCoordinator::modeReplSet) {
-                const OpTime lastOp = repl::ReplClientInfo::forClient(c).getLastOp();
+                const Timestamp lastOp = repl::ReplClientInfo::forClient(c).getLastOp();
                 if (!lastOp.isNull()) {
                     result.append("lastOp", lastOp);
                 }
@@ -139,8 +139,8 @@ namespace mongo {
             // for sharding; also useful in general for debugging
             result.appendNumber( "connectionId" , c.getConnectionId() );
 
-            OpTime lastOpTime;
-            BSONField<OpTime> wOpTimeField("wOpTime");
+            Timestamp lastOpTime;
+            BSONField<Timestamp> wOpTimeField("wOpTime");
             FieldParser::FieldState extracted = FieldParser::extract(cmdObj, wOpTimeField, 
                                                                      &lastOpTime, &errmsg);
             if (!extracted) {
diff --git a/src/mongo/db/dbcommands.cpp b/src/mongo/db/dbcommands.cpp
index 6fa03e9909a..297dd866f7d 100644
--- a/src/mongo/db/dbcommands.cpp
+++ b/src/mongo/db/dbcommands.cpp
@@ -1397,9 +1397,9 @@ namespace mongo {
     };
 
     namespace {
-        void appendGLEHelperData(BSONObjBuilder& bob, const OpTime& opTime, const OID& oid) {
+        void appendGLEHelperData(BSONObjBuilder& bob, const Timestamp& opTime, const OID& oid) {
             BSONObjBuilder subobj(bob.subobjStart(kGLEStatsFieldName));
-            subobj.appendTimestamp(kGLEStatsLastOpTimeFieldName, opTime.asDate());
+            subobj.append(kGLEStatsLastOpTimeFieldName, opTime);
             subobj.appendOID(kGLEStatsElectionIdFieldName, const_cast<OID*>(&oid));
             subobj.done();
         }
diff --git a/src/mongo/db/field_parser.cpp b/src/mongo/db/field_parser.cpp
index a53714afadb..1dbca72c2c7 100644
--- a/src/mongo/db/field_parser.cpp
+++ b/src/mongo/db/field_parser.cpp
@@ -162,16 +162,16 @@ namespace mongo {
     }
 
     FieldParser::FieldState FieldParser::extract( BSONObj doc,
-                                                  const BSONField<OpTime>& field,
-                                                  OpTime* out,
+                                                  const BSONField<Timestamp>& field,
+                                                  Timestamp* out,
                                                   string* errMsg ) {
         return extract( doc[field.name()], field, out, errMsg );
     }
 
 
     FieldParser::FieldState FieldParser::extract( BSONElement elem,
-                                                  const BSONField<OpTime>& field,
-                                                  OpTime* out,
+                                                  const BSONField<Timestamp>& field,
+                                                  Timestamp* out,
                                                   string* errMsg )
     {
         if (elem.eoo()) {
@@ -184,8 +184,8 @@ namespace mongo {
             }
         }
 
-        if (elem.type() == Timestamp) {
-            *out = elem._opTime();
+        if (elem.type() == bsonTimestamp) {
+            *out = elem.timestamp();
             return FIELD_SET;
         }
 
diff --git a/src/mongo/db/field_parser.h b/src/mongo/db/field_parser.h
index 92a3df37e39..2b8da3eaa0a 100644
--- a/src/mongo/db/field_parser.h
+++ b/src/mongo/db/field_parser.h
@@ -30,7 +30,6 @@
 
 #include <string>
 
-#include "mongo/bson/bson_field.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/s/bson_serializable.h"
 #include "mongo/util/time_support.h"
@@ -107,13 +106,13 @@ namespace mongo {
                                    std::string* errMsg = NULL );
 
         static FieldState extract( BSONObj doc,
-                                   const BSONField<OpTime>& field,
-                                   OpTime* out,
+                                   const BSONField<Timestamp>& field,
+                                   Timestamp* out,
                                    std::string* errMsg = NULL );
 
         static FieldState extract( BSONElement elem,
-                                   const BSONField<OpTime>& field,
-                                   OpTime* out,
+                                   const BSONField<Timestamp>& field,
+                                   Timestamp* out,
                                    std::string* errMsg = NULL );
 
         static FieldState extract( BSONObj doc,
diff --git a/src/mongo/db/field_parser_test.cpp b/src/mongo/db/field_parser_test.cpp
index 9e3f974c915..902b6548e64 100644
--- a/src/mongo/db/field_parser_test.cpp
+++ b/src/mongo/db/field_parser_test.cpp
@@ -30,7 +30,6 @@
 #include <vector>
 #include <map>
 
-#include "mongo/bson/bson_field.h"
 #include "mongo/db/field_parser.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/unittest/unittest.h"
diff --git a/src/mongo/db/global_optime.cpp b/src/mongo/db/global_timestamp.cpp
index 664838a179c..f6cf646ba7e 100644
--- a/src/mongo/db/global_optime.cpp
+++ b/src/mongo/db/global_timestamp.cpp
@@ -28,15 +28,17 @@
 
 #define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kDefault
 
-#include "mongo/db/global_optime.h"
+#include <boost/thread.hpp>
+
+#include "mongo/db/global_timestamp.h"
 #include "mongo/util/concurrency/mutex.h"
 #include "mongo/util/log.h"
 
 namespace {
-    mongo::mutex globalOptimeMutex;
-    mongo::OpTime globalOpTime(0, 0);
+    mongo::mutex globalTimestampMutex;
+    mongo::Timestamp globalTimestamp(0, 0);
 
-    bool skewed(const mongo::OpTime& val) {
+    bool skewed(const mongo::Timestamp& val) {
         if (val.getInc() & 0x80000000) {
             mongo::warning() << "clock skew detected  prev: " << val.getSecs()
                              << " now: " << (unsigned) time(0) << std::endl;
@@ -48,33 +50,33 @@ namespace {
 }
 
 namespace mongo {
-    void setGlobalOptime(const OpTime& newTime) {
-        boost::lock_guard<boost::mutex> lk(globalOptimeMutex);
-        globalOpTime = newTime;
+    void setGlobalTimestamp(const Timestamp& newTime) {
+        boost::lock_guard<boost::mutex> lk(globalTimestampMutex);
+        globalTimestamp = newTime;
     }
 
-    OpTime getLastSetOptime() {
-        boost::lock_guard<boost::mutex> lk(globalOptimeMutex);
-        return globalOpTime;
+    Timestamp getLastSetTimestamp() {
+        boost::lock_guard<boost::mutex> lk(globalTimestampMutex);
+        return globalTimestamp;
     }
 
-    OpTime getNextGlobalOptime() {
-        boost::lock_guard<boost::mutex> lk(globalOptimeMutex);
+    Timestamp getNextGlobalTimestamp() {
+        boost::lock_guard<boost::mutex> lk(globalTimestampMutex);
 
         const unsigned now = (unsigned) time(0);
-        const unsigned globalSecs = globalOpTime.getSecs();
+        const unsigned globalSecs = globalTimestamp.getSecs();
         if ( globalSecs == now ) {
-            globalOpTime = OpTime(globalSecs, globalOpTime.getInc() + 1);
+            globalTimestamp = Timestamp(globalSecs, globalTimestamp.getInc() + 1);
         }
         else if ( now < globalSecs ) {
-            globalOpTime = OpTime(globalSecs, globalOpTime.getInc() + 1);
+            globalTimestamp = Timestamp(globalSecs, globalTimestamp.getInc() + 1);
             // separate function to keep out of the hot code path
-            fassert(17449, !skewed(globalOpTime));
+            fassert(17449, !skewed(globalTimestamp));
         }
         else {
-            globalOpTime = OpTime(now, 1);
+            globalTimestamp = Timestamp(now, 1);
         }
 
-        return globalOpTime;
+        return globalTimestamp;
     }
 }
diff --git a/src/mongo/db/global_optime.h b/src/mongo/db/global_timestamp.h
index acb6e2d0ae6..d39a5364fd5 100644
--- a/src/mongo/db/global_optime.h
+++ b/src/mongo/db/global_timestamp.h
@@ -28,18 +28,18 @@
 
 #pragma once
 
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 
 namespace mongo {
-    void setGlobalOptime(const OpTime& newTime);
+    void setGlobalTimestamp(const Timestamp& newTime);
 
     /**
-     * Returns the value of the global OpTime generated last time or set.
+     * Returns the value of the global Timestamp generated last time or set.
      */
-    OpTime getLastSetOptime();
+    Timestamp getLastSetTimestamp();
 
     /**
-     * Generates a new and unique OpTime.
+     * Generates a new and unique Timestamp.
      */
-    OpTime getNextGlobalOptime();
+    Timestamp getNextGlobalTimestamp();
 }
diff --git a/src/mongo/db/hasher_test.cpp b/src/mongo/db/hasher_test.cpp
index 1d52e8815b0..02351127c48 100644
--- a/src/mongo/db/hasher_test.cpp
+++ b/src/mongo/db/hasher_test.cpp
@@ -345,7 +345,7 @@ namespace {
 
         BSONObj o = BSON( "check" << Date_t( 0x5566778811223344LL ) );
         ASSERT_EQUALS( hashIt( o ), 4476222765095560467LL );
-        o = builder1.append( "check", OpTime(0x55667788LL, 0x11223344LL) ).obj();
+        o = builder1.append( "check", Timestamp(0x55667788LL, 0x11223344LL) ).obj();
         ASSERT_EQUALS( hashIt( o ), 4873046866288452390LL );
 
         o = BSON( "check" << Date_t( 0 ) );
diff --git a/src/mongo/db/instance.cpp b/src/mongo/db/instance.cpp
index 1c49b54c3a1..0595cf83ede 100644
--- a/src/mongo/db/instance.cpp
+++ b/src/mongo/db/instance.cpp
@@ -59,7 +59,7 @@
 #include "mongo/db/exec/delete.h"
 #include "mongo/db/exec/update.h"
 #include "mongo/db/service_context.h"
-#include "mongo/db/global_optime.h"
+#include "mongo/db/global_timestamp.h"
 #include "mongo/db/instance.h"
 #include "mongo/db/introspect.h"
 #include "mongo/db/json.h"
@@ -828,7 +828,7 @@ namespace {
         int pass = 0;
         bool exhaust = false;
         QueryResult::View msgdata = 0;
-        OpTime last;
+        Timestamp last;
         while( 1 ) {
             bool isCursorAuthorized = false;
             try {
@@ -846,10 +846,10 @@ namespace {
                     }
 
                     if (pass == 0) {
-                        last = getLastSetOptime();
+                        last = getLastSetTimestamp();
                     }
                     else {
-                        repl::waitUpToOneSecondForOptimeChange(last);
+                        repl::waitUpToOneSecondForTimestampChange(last);
                     }
                 }
 
diff --git a/src/mongo/db/jsobj.h b/src/mongo/db/jsobj.h
index 83bb1d80879..6a4e962b683 100644
--- a/src/mongo/db/jsobj.h
+++ b/src/mongo/db/jsobj.h
@@ -43,7 +43,7 @@
 #include "mongo/platform/basic.h"
 
 #include "mongo/bson/util/builder.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/bson/bsontypes.h"
 #include "mongo/bson/oid.h"
 #include "mongo/bson/bsonelement.h"
@@ -52,5 +52,4 @@
 #include "mongo/bson/bsonobjbuilder.h"
 #include "mongo/bson/ordering.h"
 #include "mongo/base/string_data.h"
-#include "mongo/bson/bson_db.h"
 
diff --git a/src/mongo/db/json.cpp b/src/mongo/db/json.cpp
index 6369ddfe50a..8fca4e77190 100644
--- a/src/mongo/db/json.cpp
+++ b/src/mongo/db/json.cpp
@@ -555,7 +555,7 @@ namespace mongo {
         if (!readToken(RBRACE)) {
             return parseError("Expecting '}'");
         }
-        builder.append(fieldName, OpTime(seconds, count));
+        builder.append(fieldName, Timestamp(seconds, count));
         return Status::OK();
     }
 
@@ -815,7 +815,7 @@ namespace mongo {
         if (!readToken(RPAREN)) {
             return parseError("Expecting ')'");
         }
-        builder.append(fieldName, OpTime(seconds, count));
+        builder.append(fieldName, Timestamp(seconds, count));
         return Status::OK();
     }
 
diff --git a/src/mongo/db/lasterror.h b/src/mongo/db/lasterror.h
index 60cd9c1eae2..778a1653bb3 100644
--- a/src/mongo/db/lasterror.h
+++ b/src/mongo/db/lasterror.h
@@ -43,6 +43,7 @@ namespace mongo {
     static const char kUpsertedFieldName[] = "upserted";
     static const char kGLEStatsFieldName[] = "$gleStats";
     static const char kGLEStatsLastOpTimeFieldName[] = "lastOpTime";
+    static const char kGLEStatsLastOpTimeTermFieldName[] = "lastOpTimeTerm";
     static const char kGLEStatsElectionIdFieldName[] = "electionId";
 
     struct LastError {
diff --git a/src/mongo/db/ops/SConscript b/src/mongo/db/ops/SConscript
index f16faacf6e1..5c0018803a5 100644
--- a/src/mongo/db/ops/SConscript
+++ b/src/mongo/db/ops/SConscript
@@ -69,7 +69,7 @@ env.Library(
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/expressions',
-        '$BUILD_DIR/mongo/global_optime',
+        '$BUILD_DIR/mongo/global_timestamp',
         'update_common',
     ],
 )
diff --git a/src/mongo/db/ops/insert.cpp b/src/mongo/db/ops/insert.cpp
index f410962b5b3..715895830da 100644
--- a/src/mongo/db/ops/insert.cpp
+++ b/src/mongo/db/ops/insert.cpp
@@ -29,7 +29,7 @@
  */
 
 #include "mongo/db/ops/insert.h"
-#include "mongo/db/global_optime.h"
+#include "mongo/db/global_timestamp.h"
 #include "mongo/util/mongoutils/str.h"
 
 namespace mongo {
@@ -53,7 +53,7 @@ namespace mongo {
             while ( i.more() ) {
                 BSONElement e = i.next();
 
-                if ( e.type() == Timestamp && e.timestampValue() == 0 ) {
+                if ( e.type() == bsonTimestamp && e.timestampValue() == 0 ) {
                     // we replace Timestamp(0,0) at the top level with a correct value
                     // in the fast pass, we just mark that we want to swap
                     hasTimestampToFix = true;
@@ -122,8 +122,8 @@ namespace mongo {
             if ( hadId && e.fieldNameStringData() == "_id" ) {
                 // no-op
             }
-            else if ( e.type() == Timestamp && e.timestampValue() == 0 ) {
-                b.append( e.fieldName(), getNextGlobalOptime() );
+            else if ( e.type() == bsonTimestamp && e.timestampValue() == 0 ) {
+                b.append( e.fieldName(), getNextGlobalTimestamp() );
             }
             else {
                 b.append( e );
diff --git a/src/mongo/db/ops/modifier_current_date.cpp b/src/mongo/db/ops/modifier_current_date.cpp
index aa683a5404f..f38cc4e4441 100644
--- a/src/mongo/db/ops/modifier_current_date.cpp
+++ b/src/mongo/db/ops/modifier_current_date.cpp
@@ -30,7 +30,7 @@
 
 #include "mongo/base/error_codes.h"
 #include "mongo/bson/mutable/document.h"
-#include "mongo/db/global_optime.h"
+#include "mongo/db/global_timestamp.h"
 #include "mongo/db/ops/field_checker.h"
 #include "mongo/db/ops/log_builder.h"
 #include "mongo/db/ops/path_support.h"
@@ -210,7 +210,7 @@ namespace mongo {
 
             elemToSet = _typeIsDate ?
                             doc.makeElementDate(lastPart, Date_t()) :
-                            doc.makeElementTimestamp(lastPart, OpTime());
+                            doc.makeElementTimestamp(lastPart, Timestamp());
 
             if (!elemToSet.ok()) {
                 return Status(ErrorCodes::InternalError, "can't create new element");
@@ -246,7 +246,7 @@ namespace mongo {
                 return s;
         }
         else {
-            Status s = elemToSet.setValueTimestamp(getNextGlobalOptime());
+            Status s = elemToSet.setValueTimestamp(getNextGlobalTimestamp());
             if (!s.isOK())
                 return s;
         }
diff --git a/src/mongo/db/ops/modifier_current_date_test.cpp b/src/mongo/db/ops/modifier_current_date_test.cpp
index 512c857bc1b..51eb4a79659 100644
--- a/src/mongo/db/ops/modifier_current_date_test.cpp
+++ b/src/mongo/db/ops/modifier_current_date_test.cpp
@@ -43,7 +43,7 @@ namespace {
     using mongo::LogBuilder;
     using mongo::ModifierCurrentDate;
     using mongo::ModifierInterface;
-    using mongo::OpTime;
+    using mongo::Timestamp;
     using mongo::Status;
     using mongo::StringData;
     using mongo::fromjson;
@@ -220,7 +220,7 @@ namespace {
         ASSERT_FALSE(execInfo.noOp);
         ASSERT_EQUALS("a", execInfo.fieldRef[0]->dottedField());
 
-        mongo::OpTime ts;
+        mongo::Timestamp ts;
         BSONObj olderDateObj = BSON("a" << ts);
         ASSERT_OK(mod.apply());
         ASSERT_FALSE(doc.isInPlaceModeEnabled());
@@ -305,7 +305,7 @@ namespace {
         ASSERT_FALSE(execInfo.noOp);
         ASSERT_EQUALS("a", execInfo.fieldRef[0]->dottedField());
 
-        mongo::OpTime ts;
+        mongo::Timestamp ts;
         BSONObj olderDateObj = BSON("a" << ts);
         ASSERT_OK(mod.apply());
         ASSERT_TRUE(doc.isInPlaceModeEnabled()); //Same Size as Date
@@ -327,7 +327,7 @@ namespace {
         ASSERT_FALSE(execInfo.noOp);
         ASSERT_EQUALS("a.b", execInfo.fieldRef[0]->dottedField());
 
-        mongo::OpTime ts;
+        mongo::Timestamp ts;
         BSONObj olderDateObj = BSON("a" << BSON( "b" << ts));
         ASSERT_OK(mod.apply());
         ASSERT_TRUE(doc.isInPlaceModeEnabled()); //Same Size as Date
@@ -349,7 +349,7 @@ namespace {
         ASSERT_FALSE(execInfo.noOp);
         ASSERT_EQUALS("a.b", execInfo.fieldRef[0]->dottedField());
 
-        mongo::OpTime ts;
+        mongo::Timestamp ts;
         BSONObj olderDateObj = BSON("a" << BSON( "b" << ts));
         ASSERT_OK(mod.apply());
         ASSERT_FALSE(doc.isInPlaceModeEnabled());
diff --git a/src/mongo/db/ops/modifier_object_replace.cpp b/src/mongo/db/ops/modifier_object_replace.cpp
index dc714b52105..5ebbb4bd342 100644
--- a/src/mongo/db/ops/modifier_object_replace.cpp
+++ b/src/mongo/db/ops/modifier_object_replace.cpp
@@ -30,7 +30,7 @@
 
 #include "mongo/base/error_codes.h"
 #include "mongo/bson/mutable/document.h"
-#include "mongo/db/global_optime.h"
+#include "mongo/db/global_timestamp.h"
 #include "mongo/db/ops/log_builder.h"
 #include "mongo/util/mongoutils/str.h"
 
@@ -47,14 +47,15 @@ namespace mongo {
                 BSONElement e = i.next();
 
                 // Skip _id field -- we do not replace it
-                if (e.type() == Timestamp && e.fieldNameStringData() != idFieldName) {
-                    // performance note, this locks a mutex:
+                if (e.type() == bsonTimestamp && e.fieldNameStringData() != idFieldName) {
+                    // TODO(emilkie): This is not endian-safe.
                     unsigned long long &timestamp =
                         *(reinterpret_cast<unsigned long long*>(
                               const_cast<char *>(e.value())));
                     if (timestamp == 0) {
-                        OpTime ts(getNextGlobalOptime());
-                        timestamp = ts.asDate();
+                        // performance note, this locks a mutex:
+                        Timestamp ts(getNextGlobalTimestamp());
+                        timestamp = ts.asULL();
                     }
                 }
             }
diff --git a/src/mongo/db/ops/modifier_object_replace_test.cpp b/src/mongo/db/ops/modifier_object_replace_test.cpp
index 77946d11e05..3a5de50fead 100644
--- a/src/mongo/db/ops/modifier_object_replace_test.cpp
+++ b/src/mongo/db/ops/modifier_object_replace_test.cpp
@@ -34,7 +34,7 @@
 #include "mongo/bson/mutable/algorithm.h"
 #include "mongo/bson/mutable/document.h"
 #include "mongo/bson/mutable/mutable_bson_test_utils.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/json.h"
 #include "mongo/db/ops/log_builder.h"
diff --git a/src/mongo/db/pipeline/document_value_test.cpp b/src/mongo/db/pipeline/document_value_test.cpp
index 28e63419242..0deb17f7341 100644
--- a/src/mongo/db/pipeline/document_value_test.cpp
+++ b/src/mongo/db/pipeline/document_value_test.cpp
@@ -375,7 +375,7 @@ namespace DocumentTests {
                 append("codeWScope", BSONCodeWScope("asdf", BSONObj()));
                 append("codeWScopeWScope", BSONCodeWScope("asdf", BSON("one" << 1)));
                 append("int", 1);
-                append("timestamp", OpTime());
+                append("timestamp", Timestamp());
                 append("long", 1LL);
                 append("very long", 1LL << 40);
                 append("maxkey", MAXKEY);
@@ -533,12 +533,12 @@ namespace DocumentTests {
         };
         
         /** Timestamp type. */
-        class Timestamp {
+        class JSTimestamp {
         public:
             void run() {
-                Value value = Value( OpTime( 777 ) );
-                ASSERT( OpTime( 777 ) == value.getTimestamp() );
-                ASSERT_EQUALS( mongo::Timestamp, value.getType() );
+                Value value = Value( Timestamp( 777 ) );
+                ASSERT( Timestamp( 777 ) == value.getTimestamp() );
+                ASSERT_EQUALS( mongo::bsonTimestamp, value.getType() );
                 assertRoundTrips( value );
             }
         };
@@ -1024,7 +1024,7 @@ namespace DocumentTests {
              */
             class TimestampToDate : public ToDateBase {
                 Value value() {
-                    return Value( OpTime( 777, 666 ) );
+                    return Value( Timestamp( 777, 666 ) );
                 }
                 long long expected() { return 777 * 1000; }
             };
@@ -1076,9 +1076,9 @@ namespace DocumentTests {
             /** Coerce timestamp to string. */
             class TimestampToString : public ToStringBase {
                 Value value() {
-                    return Value( OpTime( 1, 2 ) );
+                    return Value( Timestamp( 1, 2 ) );
                 }
-                string expected() { return OpTime( 1, 2 ).toStringPretty(); }
+                string expected() { return Timestamp( 1, 2 ).toStringPretty(); }
             };
             
             /** Coerce date to string. */
@@ -1111,8 +1111,8 @@ namespace DocumentTests {
             class TimestampToTimestamp {
             public:
                 void run() {
-                    Value value = Value( OpTime( 1010 ) );
-                    ASSERT( OpTime( 1010 ) == value.coerceToTimestamp() );
+                    Value value = Value( Timestamp( 1010 ) );
+                    ASSERT( Timestamp( 1010 ) == value.coerceToTimestamp() );
                 }
             };
 
@@ -1272,8 +1272,8 @@ namespace DocumentTests {
                 assertComparison( -1, fromjson( "{'':/a/}" ), fromjson( "{'':/aa/}" ) );
 
                 // Timestamp.
-                assertComparison( 0, OpTime( 1234 ), OpTime( 1234 ) );
-                assertComparison( -1, OpTime( 4 ), OpTime( 1234 ) );
+                assertComparison( 0, Timestamp( 1234 ), Timestamp( 1234 ) );
+                assertComparison( -1, Timestamp( 4 ), Timestamp( 1234 ) );
 
                 // Cross-type comparisons. Listed in order of canonical types.
                 assertComparison(-1, Value(mongo::MINKEY), Value());
@@ -1291,8 +1291,8 @@ namespace DocumentTests {
                 assertComparison(-1, Value(BSONBinData("", 0, MD5Type)), Value(mongo::OID()));
                 assertComparison(-1, Value(mongo::OID()), Value(false));
                 assertComparison(-1, Value(false), Value(Date_t(0)));
-                assertComparison(-1, Value(Date_t(0)), Value(OpTime()));
-                assertComparison(-1, Value(OpTime()), Value(BSONRegEx("")));
+                assertComparison(-1, Value(Date_t(0)), Value(Timestamp()));
+                assertComparison(-1, Value(Timestamp()), Value(BSONRegEx("")));
                 assertComparison(-1, Value(BSONRegEx("")), Value(BSONDBRef("", mongo::OID())));
                 assertComparison(-1, Value(BSONDBRef("", mongo::OID())), Value(BSONCode("")));
                 assertComparison(-1, Value(BSONCode("")), Value(BSONCodeWScope("", BSONObj())));
@@ -1303,11 +1303,11 @@ namespace DocumentTests {
             void assertComparison( int expectedResult, const T& a, const U& b ) {
                 assertComparison( expectedResult, BSON( "" << a ), BSON( "" << b ) );
             }
-            void assertComparison( int expectedResult, const OpTime& a, const OpTime& b ) {
+            void assertComparison( int expectedResult, const Timestamp& a, const Timestamp& b ) {
                 BSONObjBuilder first;
-                first.appendTimestamp( "", a.asDate() );
+                first.append( "", a );
                 BSONObjBuilder second;
-                second.appendTimestamp( "", b.asDate() );
+                second.append( "", b );
                 assertComparison( expectedResult, first.obj(), second.obj() );
             }
             int sign(int cmp) {
@@ -1433,7 +1433,7 @@ namespace DocumentTests {
             add<Value::String>();
             add<Value::StringWithNull>();
             add<Value::Date>();
-            add<Value::Timestamp>();
+            add<Value::JSTimestamp>();
             add<Value::EmptyDocument>();
             add<Value::EmptyArray>();
             add<Value::Array>();
diff --git a/src/mongo/db/pipeline/value.cpp b/src/mongo/db/pipeline/value.cpp
index f96e8c0aeca..8ef22166e84 100644
--- a/src/mongo/db/pipeline/value.cpp
+++ b/src/mongo/db/pipeline/value.cpp
@@ -56,7 +56,7 @@ namespace mongo {
         case MaxKey:
         case jstOID:
         case Date:
-        case Timestamp:
+        case bsonTimestamp:
         case EOO:
         case jstNULL:
         case Undefined:
@@ -199,8 +199,8 @@ namespace mongo {
             _storage.intValue = elem.numberInt();
             break;
 
-        case Timestamp:
-            _storage.timestampValue = elem._opTime().asDate();
+        case bsonTimestamp:
+            _storage.timestampValue = elem.timestamp().asULL();
             break;
 
         case NumberLong:
@@ -289,7 +289,7 @@ namespace mongo {
         case String:       return builder << val.getStringData();
         case Bool:         return builder << val.getBool();
         case Date:         return builder << Date_t(val.getDate());
-        case Timestamp:    return builder << val.getTimestamp();
+        case bsonTimestamp:    return builder << val.getTimestamp();
         case Object:       return builder << val.getDocument();
         case Symbol:       return builder << BSONSymbol(val.getStringData());
         case Code:         return builder << BSONCode(val.getStringData());
@@ -347,7 +347,7 @@ namespace mongo {
         case Date:
         case RegEx:
         case Symbol:
-        case Timestamp:
+        case bsonTimestamp:
             return true;
 
         case EOO:
@@ -425,7 +425,7 @@ namespace mongo {
         case Date:
             return getDate();
 
-        case Timestamp:
+        case bsonTimestamp:
             return getTimestamp().getSecs() * 1000LL;
 
         default:
@@ -502,7 +502,7 @@ namespace mongo {
         case String:
             return getStringData().toString();
 
-        case Timestamp:
+        case bsonTimestamp:
             return getTimestamp().toStringPretty();
 
         case Date:
@@ -521,9 +521,9 @@ namespace mongo {
         } // switch(getType())
     }
 
-    OpTime Value::coerceToTimestamp() const {
+    Timestamp Value::coerceToTimestamp() const {
         switch(getType()) {
-        case Timestamp:
+        case bsonTimestamp:
             return getTimestamp();
 
         default:
@@ -578,7 +578,7 @@ namespace mongo {
         case Bool:
             return rL.getBool() - rR.getBool();
 
-        case Timestamp: // unsigned
+        case bsonTimestamp: // unsigned
             return cmp(rL._storage.timestampValue, rR._storage.timestampValue);
 
         case Date: // signed
@@ -705,7 +705,7 @@ namespace mongo {
             boost::hash_combine(seed, getBool());
             break;
 
-        case Timestamp:
+        case bsonTimestamp:
         case Date:
             BOOST_STATIC_ASSERT(sizeof(_storage.dateValue) == sizeof(_storage.timestampValue));
             boost::hash_combine(seed, _storage.dateValue);
@@ -864,7 +864,7 @@ namespace mongo {
         case Bool:
         case Date:
         case NumberInt:
-        case Timestamp:
+        case bsonTimestamp:
         case NumberLong:
         case jstNULL:
         case Undefined:
@@ -897,7 +897,7 @@ namespace mongo {
         case jstNULL: return out << "null";
         case Undefined: return out << "undefined";
         case Date: return out << tmToISODateString(val.coerceToTm());
-        case Timestamp: return out << val.getTimestamp().toString();
+        case bsonTimestamp: return out << val.getTimestamp().toString();
         case Object: return out << val.getDocument().toString();
         case Array: {
             out << "[";
@@ -948,7 +948,7 @@ namespace mongo {
         case NumberDouble: buf.appendNum(_storage.doubleValue); break;
         case Bool:         buf.appendChar(_storage.boolValue); break;
         case Date:         buf.appendNum(_storage.dateValue); break;
-        case Timestamp:    buf.appendStruct(getTimestamp()); break;
+        case bsonTimestamp:    buf.appendStruct(getTimestamp()); break;
 
         // types that are like strings
         case String:
@@ -1019,7 +1019,7 @@ namespace mongo {
         case NumberDouble: return Value(buf.read<double>());
         case Bool:         return Value(bool(buf.read<char>()));
         case Date:         return Value(Date_t(buf.read<long long>()));
-        case Timestamp:    return Value(buf.read<OpTime>());
+        case bsonTimestamp:  return Value(buf.read<Timestamp>());
 
         // types that are like strings
         case String:
diff --git a/src/mongo/db/pipeline/value.h b/src/mongo/db/pipeline/value.h
index dc10ea3246e..4e30c30564d 100644
--- a/src/mongo/db/pipeline/value.h
+++ b/src/mongo/db/pipeline/value.h
@@ -72,7 +72,7 @@ namespace mongo {
         explicit Value(int value)                 : _storage(NumberInt, value) {}
         explicit Value(long long value)           : _storage(NumberLong, value) {}
         explicit Value(double value)              : _storage(NumberDouble, value) {}
-        explicit Value(const OpTime& value)       : _storage(Timestamp, value) {}
+        explicit Value(const Timestamp& value)    : _storage(bsonTimestamp, value) {}
         explicit Value(const OID& value)          : _storage(jstOID, value) {}
         explicit Value(StringData value)   : _storage(String, value) {}
         explicit Value(const std::string& value)       : _storage(String, StringData(value)) {}
@@ -150,7 +150,7 @@ namespace mongo {
         OID getOid() const;
         bool getBool() const;
         long long getDate() const; // in milliseconds
-        OpTime getTimestamp() const;
+        Timestamp getTimestamp() const;
         const char* getRegex() const;
         const char* getRegexFlags() const;
         std::string getSymbol() const;
@@ -189,7 +189,7 @@ namespace mongo {
         int coerceToInt() const;
         long long coerceToLong() const;
         double coerceToDouble() const;
-        OpTime coerceToTimestamp() const;
+        Timestamp coerceToTimestamp() const;
         long long coerceToDate() const;
         time_t coerceToTimeT() const;
         tm coerceToTm() const; // broken-out time struct (see man gmtime)
@@ -326,8 +326,8 @@ namespace mongo {
         return _storage.dateValue;
     }
 
-    inline OpTime Value::getTimestamp() const {
-        verify(getType() == Timestamp);
+    inline Timestamp Value::getTimestamp() const {
+        verify(getType() == bsonTimestamp);
         return Date_t(_storage.timestampValue);
     }
 
diff --git a/src/mongo/db/pipeline/value_internal.h b/src/mongo/db/pipeline/value_internal.h
index 910728019ce..834c2e7d1d6 100644
--- a/src/mongo/db/pipeline/value_internal.h
+++ b/src/mongo/db/pipeline/value_internal.h
@@ -37,7 +37,7 @@
 #include "mongo/bson/oid.h"
 #include "mongo/util/debug_util.h"
 #include "mongo/util/intrusive_counter.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 
 
 namespace mongo {
@@ -81,7 +81,7 @@ namespace mongo {
         ValueStorage(BSONType t, int i)                    { zero(); type = t; intValue = i; }
         ValueStorage(BSONType t, long long l)              { zero(); type = t; longValue = l; }
         ValueStorage(BSONType t, double d)                 { zero(); type = t; doubleValue = d; }
-        ValueStorage(BSONType t, OpTime r)        { zero(); type = t; timestampValue = r.asDate(); }
+        ValueStorage(BSONType t, Timestamp r)     { zero(); type = t; timestampValue = r.asULL(); }
         ValueStorage(BSONType t, bool b)                   { zero(); type = t; boolValue = b; }
         ValueStorage(BSONType t, const Document& d)        { zero(); type = t; putDocument(d); }
         ValueStorage(BSONType t, const RCVector* a)        { zero(); type = t; putVector(a); }
diff --git a/src/mongo/db/query/find.cpp b/src/mongo/db/query/find.cpp
index fb6218fc800..a6a13db1fc8 100644
--- a/src/mongo/db/query/find.cpp
+++ b/src/mongo/db/query/find.cpp
@@ -377,7 +377,7 @@ namespace mongo {
             }
 
             // If we're replaying the oplog, we save the last time that we read.
-            OpTime slaveReadTill;
+            Timestamp slaveReadTill;
 
             // What number result are we starting at?  Used to fill out the reply.
             startingResult = cc->pos();
@@ -401,8 +401,8 @@ namespace mongo {
                 // Possibly note slave's position in the oplog.
                 if (queryOptions & QueryOption_OplogReplay) {
                     BSONElement e = obj["ts"];
-                    if (Date == e.type() || Timestamp == e.type()) {
-                        slaveReadTill = e._opTime();
+                    if (Date == e.type() || bsonTimestamp == e.type()) {
+                        slaveReadTill = e.timestamp();
                     }
                 }
 
@@ -615,7 +615,7 @@ namespace mongo {
         int numResults = 0;
 
         // If we're replaying the oplog, we save the last time that we read.
-        OpTime slaveReadTill;
+        Timestamp slaveReadTill;
 
         BSONObj obj;
         PlanExecutor::ExecState state;
@@ -634,8 +634,8 @@ namespace mongo {
             // Possibly note slave's position in the oplog.
             if (pq.isOplogReplay()) {
                 BSONElement e = obj["ts"];
-                if (Date == e.type() || Timestamp == e.type()) {
-                    slaveReadTill = e._opTime();
+                if (Date == e.type() || bsonTimestamp == e.type()) {
+                    slaveReadTill = e.timestamp();
                 }
             }
 
diff --git a/src/mongo/db/query/get_executor.cpp b/src/mongo/db/query/get_executor.cpp
index 6e3af1c474b..202be486a68 100644
--- a/src/mongo/db/query/get_executor.cpp
+++ b/src/mongo/db/query/get_executor.cpp
@@ -556,8 +556,8 @@ namespace {
 
         // See if the RecordStore supports the oplogStartHack
         const BSONElement tsElem = extractOplogTsOptime(tsExpr);
-        if (tsElem.type() == Timestamp) {
-            StatusWith<RecordId> goal = oploghack::keyForOptime(tsElem._opTime());
+        if (tsElem.type() == bsonTimestamp) {
+            StatusWith<RecordId> goal = oploghack::keyForOptime(tsElem.timestamp());
             if (goal.isOK()) {
                 startLoc = collection->getRecordStore()->oplogStartHack(txn, goal.getValue());
             }
diff --git a/src/mongo/db/repl/SConscript b/src/mongo/db/repl/SConscript
index e8d797785de..725740ec022 100644
--- a/src/mongo/db/repl/SConscript
+++ b/src/mongo/db/repl/SConscript
@@ -90,7 +90,7 @@ env.Library('repl_coordinator_impl',
                      '$BUILD_DIR/mongo/db/common',
                      '$BUILD_DIR/mongo/db/index/index_descriptor',
                      '$BUILD_DIR/mongo/fail_point',
-                     '$BUILD_DIR/mongo/global_optime',
+                     '$BUILD_DIR/mongo/global_timestamp',
                      '$BUILD_DIR/mongo/server_options_core',
                      '$BUILD_DIR/mongo/service_context',
                      '$BUILD_DIR/mongo/util/net/command_status',
diff --git a/src/mongo/db/repl/bgsync.cpp b/src/mongo/db/repl/bgsync.cpp
index ad2833df368..7cdd1d42a2a 100644
--- a/src/mongo/db/repl/bgsync.cpp
+++ b/src/mongo/db/repl/bgsync.cpp
@@ -228,7 +228,7 @@ namespace {
 
 
         // find a target to sync from the last optime fetched
-        OpTime lastOpTimeFetched;
+        Timestamp lastOpTimeFetched;
         {
             boost::unique_lock<boost::mutex> lock(_mutex);
             lastOpTimeFetched = _lastOpTimeFetched;
@@ -354,7 +354,7 @@ namespace {
             {
                 boost::unique_lock<boost::mutex> lock(_mutex);
                 _lastFetchedHash = o["h"].numberLong();
-                _lastOpTimeFetched = o["ts"]._opTime();
+                _lastOpTimeFetched = o["ts"].timestamp();
                 LOG(3) << "lastOpTimeFetched: " << _lastOpTimeFetched.toStringPretty();
             }
         }
@@ -402,7 +402,7 @@ namespace {
                     sleepsecs(2);
                     return true;
                 }
-                OpTime theirTS = theirLastOp["ts"]._opTime();
+                Timestamp theirTS = theirLastOp["ts"].timestamp();
                 if (theirTS < _lastOpTimeFetched) {
                     log() << "we are ahead of the sync source, will try to roll back";
                     syncRollback(txn, _replCoord->getMyLastOptime(), &r, _replCoord);
@@ -420,7 +420,7 @@ namespace {
         }
 
         BSONObj o = r.nextSafe();
-        OpTime ts = o["ts"]._opTime();
+        Timestamp ts = o["ts"].timestamp();
         long long hash = o["h"].numberLong();
         if( ts != _lastOpTimeFetched || hash != _lastFetchedHash ) {
             log() << "our last op time fetched: " << _lastOpTimeFetched.toStringPretty();
@@ -447,7 +447,7 @@ namespace {
 
         _pause = true;
         _syncSourceHost = HostAndPort();
-        _lastOpTimeFetched = OpTime(0,0);
+        _lastOpTimeFetched = Timestamp(0,0);
         _lastFetchedHash = 0;
         _appliedBufferCondition.notify_all();
         _pausedCondition.notify_all();
diff --git a/src/mongo/db/repl/bgsync.h b/src/mongo/db/repl/bgsync.h
index 8a36e572abe..7537e0e8606 100644
--- a/src/mongo/db/repl/bgsync.h
+++ b/src/mongo/db/repl/bgsync.h
@@ -131,7 +131,7 @@ namespace repl {
         // _mutex protects all of the class variables except _syncSourceReader and _buffer
         mutable boost::mutex _mutex;
 
-        OpTime _lastOpTimeFetched;
+        Timestamp _lastOpTimeFetched;
 
         // lastAppliedHash is used to generate a new hash for the following op, when primary.
         long long _lastAppliedHash;
diff --git a/src/mongo/db/repl/freshness_checker.cpp b/src/mongo/db/repl/freshness_checker.cpp
index 3f533e28f6e..ebe3d59b67b 100644
--- a/src/mongo/db/repl/freshness_checker.cpp
+++ b/src/mongo/db/repl/freshness_checker.cpp
@@ -33,7 +33,7 @@
 #include "mongo/db/repl/freshness_checker.h"
 
 #include "mongo/base/status.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/repl/member_heartbeat_data.h"
 #include "mongo/db/repl/replica_set_config.h"
 #include "mongo/db/repl/replication_executor.h"
@@ -47,7 +47,7 @@ namespace mongo {
 namespace repl {
 
     FreshnessChecker::Algorithm::Algorithm(
-            OpTime lastOpTimeApplied,
+            Timestamp lastOpTimeApplied,
             const ReplicaSetConfig& rsConfig,
             int selfIndex,
             const std::vector<HostAndPort>& targets) :
@@ -88,7 +88,7 @@ namespace repl {
         BSONObjBuilder freshCmdBuilder;
         freshCmdBuilder.append("replSetFresh", 1);
         freshCmdBuilder.append("set", _rsConfig.getReplSetName());
-        freshCmdBuilder.append("opTime", Date_t(_lastOpTimeApplied.asDate()));
+        freshCmdBuilder.append("opTime", Date_t(_lastOpTimeApplied.asULL()));
         freshCmdBuilder.append("who", selfConfig.getHostAndPort().toString());
         freshCmdBuilder.appendIntOrLL("cfgver", _rsConfig.getConfigVersion());
         freshCmdBuilder.append("id", selfConfig.getId());
@@ -169,7 +169,7 @@ namespace repl {
             _abortReason = FresherNodeFound;
             return;
         }
-        OpTime remoteTime(res["opTime"].date());
+        Timestamp remoteTime(res["opTime"].date());
         if (remoteTime == _lastOpTimeApplied) {
             _abortReason = FreshnessTie;
         }
@@ -216,7 +216,7 @@ namespace repl {
 
     StatusWith<ReplicationExecutor::EventHandle> FreshnessChecker::start(
             ReplicationExecutor* executor,
-            const OpTime& lastOpTimeApplied,
+            const Timestamp& lastOpTimeApplied,
             const ReplicaSetConfig& currentConfig,
             int selfIndex,
             const std::vector<HostAndPort>& targets,
diff --git a/src/mongo/db/repl/freshness_checker.h b/src/mongo/db/repl/freshness_checker.h
index 71f82cb86d3..3570ee8b051 100644
--- a/src/mongo/db/repl/freshness_checker.h
+++ b/src/mongo/db/repl/freshness_checker.h
@@ -32,7 +32,7 @@
 #include <vector>
 
 #include "mongo/base/disallow_copying.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/repl/replica_set_config.h"
 #include "mongo/db/repl/replication_executor.h"
 #include "mongo/db/repl/scatter_gather_algorithm.h"
@@ -59,7 +59,7 @@ namespace repl {
 
         class Algorithm : public ScatterGatherAlgorithm {
         public:
-            Algorithm(OpTime lastOpTimeApplied,
+            Algorithm(Timestamp lastOpTimeApplied,
                       const ReplicaSetConfig& rsConfig,
                       int selfIndex,
                       const std::vector<HostAndPort>& targets);
@@ -84,8 +84,8 @@ namespace repl {
             // Number of failed voter responses so far.
             int _failedVoterResponses;
 
-            // Last OpTime applied by the caller; used in the Fresh command 
-            const OpTime _lastOpTimeApplied;
+            // Last Timestamp applied by the caller; used in the Fresh command 
+            const Timestamp _lastOpTimeApplied;
 
             // Config to use for this check
             const ReplicaSetConfig _rsConfig;
@@ -124,7 +124,7 @@ namespace repl {
          **/
         StatusWith<ReplicationExecutor::EventHandle> start(
             ReplicationExecutor* executor,
-            const OpTime& lastOpTimeApplied,
+            const Timestamp& lastOpTimeApplied,
             const ReplicaSetConfig& currentConfig,
             int selfIndex,
             const std::vector<HostAndPort>& targets,
diff --git a/src/mongo/db/repl/freshness_checker_test.cpp b/src/mongo/db/repl/freshness_checker_test.cpp
index 362b4746606..2a7480e8d56 100644
--- a/src/mongo/db/repl/freshness_checker_test.cpp
+++ b/src/mongo/db/repl/freshness_checker_test.cpp
@@ -59,7 +59,7 @@ namespace {
 
     class FreshnessCheckerTest : public mongo::unittest::Test {
     protected:
-        void startTest(const OpTime& lastOpTimeApplied,
+        void startTest(const Timestamp& lastOpTimeApplied,
                        const ReplicaSetConfig& currentConfig,
                        int selfIndex,
                        const std::vector<HostAndPort>& hosts);
@@ -80,7 +80,7 @@ namespace {
 
     private:
         void freshnessCheckerRunner(const ReplicationExecutor::CallbackData& data,
-                                    const OpTime& lastOpTimeApplied,
+                                    const Timestamp& lastOpTimeApplied,
                                     const ReplicaSetConfig& currentConfig,
                                     int selfIndex,
                                     const std::vector<HostAndPort>& hosts);
@@ -120,12 +120,12 @@ namespace {
     }
 
     const BSONObj makeFreshRequest(const ReplicaSetConfig& rsConfig, 
-                                   OpTime lastOpTimeApplied, 
+                                   Timestamp lastOpTimeApplied, 
                                    int selfIndex) {
         const MemberConfig& myConfig = rsConfig.getMemberAt(selfIndex);
         return BSON("replSetFresh" << 1 <<
                     "set" << rsConfig.getReplSetName() <<
-                    "opTime" << Date_t(lastOpTimeApplied.asDate()) <<
+                    "opTime" << Date_t(lastOpTimeApplied.asULL()) <<
                     "who" << myConfig.getHostAndPort().toString() <<
                     "cfgver" << rsConfig.getConfigVersion() <<
                     "id" << myConfig.getId());
@@ -135,7 +135,7 @@ namespace {
     // for correct concurrency operation.
     void FreshnessCheckerTest::freshnessCheckerRunner(
             const ReplicationExecutor::CallbackData& data,
-            const OpTime& lastOpTimeApplied,
+            const Timestamp& lastOpTimeApplied,
             const ReplicaSetConfig& currentConfig,
             int selfIndex,
             const std::vector<HostAndPort>& hosts) {
@@ -149,7 +149,7 @@ namespace {
         _checkerDoneEvent = assertGet(evh);
     }
 
-    void FreshnessCheckerTest::startTest(const OpTime& lastOpTimeApplied,
+    void FreshnessCheckerTest::startTest(const Timestamp& lastOpTimeApplied,
                                          const ReplicaSetConfig& currentConfig,
                                          int selfIndex,
                                          const std::vector<HostAndPort>& hosts) {
@@ -176,9 +176,9 @@ namespace {
 
         std::vector<HostAndPort> hosts;
         hosts.push_back(config.getMemberAt(1).getHostAndPort());
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(0,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(0,0), 0);
 
-        startTest(OpTime(0, 0), config, 0, hosts);
+        startTest(Timestamp(0, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         _net->enterNetwork();
         for (size_t i = 0; i < hosts.size(); ++i) {
@@ -195,7 +195,7 @@ namespace {
                                                 "set" << "rs0" <<
                                                 "who" << "h1" <<
                                                 "cfgver" << 1 <<
-                                                "opTime" << Date_t(OpTime(0,0).asDate())),
+                                                "opTime" << Date_t(Timestamp(0,0).asULL())),
                                            Milliseconds(8))));
         }
         _net->runUntil(startDate + 10);
@@ -218,7 +218,7 @@ namespace {
         hosts.push_back(config.getMemberAt(1).getHostAndPort());
 
         startTest(
-                OpTime(0, 0),
+                Timestamp(0, 0),
                 config,
                 0,
                 hosts);
@@ -244,9 +244,9 @@ namespace {
         std::vector<HostAndPort> hosts;
         hosts.push_back(config.getMemberAt(1).getHostAndPort());
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(10,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(10,0), 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         _net->enterNetwork();
         for (size_t i = 0; i < hosts.size(); ++i) {
@@ -264,7 +264,7 @@ namespace {
                                                 "who" << "h1" <<
                                                 "cfgver" << 1 <<
                                                 "fresher" << true <<
-                                                "opTime" << Date_t(OpTime(0,0).asDate())),
+                                                "opTime" << Date_t(Timestamp(0,0).asULL())),
                                            Milliseconds(8))));
         }
         _net->runUntil(startDate + 10);
@@ -290,9 +290,9 @@ namespace {
         std::vector<HostAndPort> hosts;
         hosts.push_back(config.getMemberAt(1).getHostAndPort());
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(0,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(0,0), 0);
 
-        startTest(OpTime(0, 0), config, 0, hosts);
+        startTest(Timestamp(0, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         _net->enterNetwork();
         for (size_t i = 0; i < hosts.size(); ++i) {
@@ -309,7 +309,7 @@ namespace {
                                                 "set" << "rs0" <<
                                                 "who" << "h1" <<
                                                 "cfgver" << 1 <<
-                                                "opTime" << Date_t(OpTime(10,0).asDate())),
+                                                "opTime" << Date_t(Timestamp(10,0).asULL())),
                                            Milliseconds(8))));
         }
         _net->runUntil(startDate + 10);
@@ -334,9 +334,9 @@ namespace {
         std::vector<HostAndPort> hosts;
         hosts.push_back(config.getMemberAt(1).getHostAndPort());
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(10,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(10,0), 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         _net->enterNetwork();
         for (size_t i = 0; i < hosts.size(); ++i) {
@@ -381,9 +381,9 @@ namespace {
         std::vector<HostAndPort> hosts;
         hosts.push_back(config.getMemberAt(1).getHostAndPort());
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(10,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(10,0), 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         _net->enterNetwork();
         for (size_t i = 0; i < hosts.size(); ++i) {
@@ -402,7 +402,7 @@ namespace {
                                                 "cfgver" << 1 <<
                                                 "veto" << true <<
                                                 "errmsg" << "I'd rather you didn't" <<
-                                                "opTime" << Date_t(OpTime(0,0).asDate())),
+                                                "opTime" << Date_t(Timestamp(0,0).asULL())),
                                            Milliseconds(8))));
         }
         _net->runUntil(startDate + 10);
@@ -443,9 +443,9 @@ namespace {
             hosts.push_back(mem->getHostAndPort());
         }
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(10,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(10,0), 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         unordered_set<HostAndPort> seen;
         _net->enterNetwork();
@@ -462,7 +462,7 @@ namespace {
                 "set" << "rs0" <<
                 "who" << target.toString() <<
                 "cfgver" << 1 <<
-                "opTime" << Date_t(OpTime(0,0).asDate());
+                "opTime" << Date_t(Timestamp(0,0).asULL());
             if (target.host() == "h1") {
                 responseBuilder << "fresher" << true;
             }
@@ -505,9 +505,9 @@ namespace {
             hosts.push_back(mem->getHostAndPort());
         }
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(10,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(10,0), 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         unordered_set<HostAndPort> seen;
         _net->enterNetwork();
@@ -526,7 +526,7 @@ namespace {
                     "set" << "rs0" <<
                     "who" << target.toString() <<
                     "cfgver" << 1 <<
-                    "opTime" << Date_t(OpTime(20,0).asDate());
+                    "opTime" << Date_t(Timestamp(20,0).asULL());
                 _net->scheduleResponse(
                         noi,
                         startDate + 20,
@@ -541,7 +541,7 @@ namespace {
                     "set" << "rs0" <<
                     "who" << target.toString() <<
                     "cfgver" << 1 <<
-                    "opTime" << Date_t(OpTime(10,0).asDate());
+                    "opTime" << Date_t(Timestamp(10,0).asULL());
                 _net->scheduleResponse(
                         noi,
                         startDate + 10,
@@ -581,9 +581,9 @@ namespace {
             hosts.push_back(mem->getHostAndPort());
         }
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(10,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(10,0), 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         unordered_set<HostAndPort> seen;
         _net->enterNetwork();
@@ -604,7 +604,7 @@ namespace {
                 responseBuilder << "opTime" << 3;
             }
             else {
-                responseBuilder << "opTime" << Date_t(OpTime(0,0).asDate());
+                responseBuilder << "opTime" << Date_t(Timestamp(0,0).asULL());
             }
             _net->scheduleResponse(
                     noi,
@@ -643,9 +643,9 @@ namespace {
             hosts.push_back(mem->getHostAndPort());
         }
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(10,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(10,0), 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         unordered_set<HostAndPort> seen;
         _net->enterNetwork();
@@ -662,7 +662,7 @@ namespace {
                 "set" << "rs0" <<
                 "who" << target.toString() <<
                 "cfgver" << 1 <<
-                "opTime" << Date_t(OpTime(0,0).asDate());
+                "opTime" << Date_t(Timestamp(0,0).asULL());
             if (target.host() == "h1") {
                 responseBuilder << "veto" << true << "errmsg" << "I'd rather you didn't";
             }
@@ -706,9 +706,9 @@ namespace {
             hosts.push_back(mem->getHostAndPort());
         }
 
-        const BSONObj freshRequest = makeFreshRequest(config, OpTime(10,0), 0);
+        const BSONObj freshRequest = makeFreshRequest(config, Timestamp(10,0), 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         unordered_set<HostAndPort> seen;
         _net->enterNetwork();
@@ -729,7 +729,7 @@ namespace {
                     "cfgver" << 1 <<
                     "veto" << true <<
                     "errmsg" << "I'd rather you didn't" <<
-                    "opTime" << Date_t(OpTime(10,0).asDate());
+                    "opTime" << Date_t(Timestamp(10,0).asULL());
                 _net->scheduleResponse(
                         noi,
                         startDate + 20,
@@ -744,7 +744,7 @@ namespace {
                     "set" << "rs0" <<
                     "who" << target.toString() <<
                     "cfgver" << 1 <<
-                    "opTime" << Date_t(OpTime(10,0).asDate());
+                    "opTime" << Date_t(Timestamp(10,0).asULL());
                 _net->scheduleResponse(
                         noi,
                         startDate + 10,
@@ -785,10 +785,10 @@ namespace {
             hosts.push_back(mem->getHostAndPort());
         }
 
-        const OpTime lastOpTimeApplied(10,0);
+        const Timestamp lastOpTimeApplied(10,0);
         const BSONObj freshRequest = makeFreshRequest(config, lastOpTimeApplied, 0);
 
-        startTest(OpTime(10, 0), config, 0, hosts);
+        startTest(Timestamp(10, 0), config, 0, hosts);
         const Date_t startDate = _net->now();
         unordered_set<HostAndPort> seen;
         _net->enterNetwork();
@@ -812,7 +812,7 @@ namespace {
                     "set" << "rs0" <<
                     "who" << target.toString() <<
                     "cfgver" << 1 <<
-                    "opTime" << Date_t(OpTime(0,0).asDate());
+                    "opTime" << Date_t(Timestamp(0,0).asULL());
                 _net->scheduleResponse(
                         noi,
                         startDate + 10,
@@ -832,7 +832,7 @@ namespace {
     public:
         virtual void setUp() {
             int selfConfigIndex = 0;
-            OpTime lastOpTimeApplied(100, 0);
+            Timestamp lastOpTimeApplied(100, 0);
 
             ReplicaSetConfig config;
             config.initialize(BSON("_id" << "rs0" <<
@@ -876,14 +876,14 @@ namespace {
         ResponseStatus lessFresh() {
             BSONObjBuilder bb;
             bb.append("ok", 1.0);
-            bb.appendDate("opTime", OpTime(10, 0).asDate());
+            bb.appendDate("opTime", Timestamp(10, 0).asULL());
             return ResponseStatus(NetworkInterfaceMock::Response(bb.obj(), Milliseconds(10)));
         }
 
         ResponseStatus moreFreshViaOpTime() {
             BSONObjBuilder bb;
             bb.append("ok", 1.0);
-            bb.appendDate("opTime", OpTime(110, 0).asDate());
+            bb.appendDate("opTime", Timestamp(110, 0).asULL());
             return ResponseStatus(NetworkInterfaceMock::Response(bb.obj(), Milliseconds(10)));
         }
 
@@ -905,7 +905,7 @@ namespace {
         ResponseStatus tiedForFreshness() {
             BSONObjBuilder bb;
             bb.append("ok", 1.0);
-            bb.appendDate("opTime", OpTime(100, 0).asDate());
+            bb.appendDate("opTime", Timestamp(100, 0).asULL());
             return ResponseStatus(NetworkInterfaceMock::Response(bb.obj(), Milliseconds(10)));
         }
 
diff --git a/src/mongo/db/repl/initial_sync.cpp b/src/mongo/db/repl/initial_sync.cpp
index 494094862ba..2af2810db29 100644
--- a/src/mongo/db/repl/initial_sync.cpp
+++ b/src/mongo/db/repl/initial_sync.cpp
@@ -48,7 +48,7 @@ namespace repl {
 
     /* initial oplog application, during initial sync, after cloning.
     */
-    void InitialSync::oplogApplication(OperationContext* txn, const OpTime& endOpTime) {
+    void InitialSync::oplogApplication(OperationContext* txn, const Timestamp& endOpTime) {
         if (replSetForceInitialSyncFailure > 0) {
             log() << "test code invoked, forced InitialSync failure: "
                   << replSetForceInitialSyncFailure;
diff --git a/src/mongo/db/repl/initial_sync.h b/src/mongo/db/repl/initial_sync.h
index 69e99524b3e..593cefa3acf 100644
--- a/src/mongo/db/repl/initial_sync.h
+++ b/src/mongo/db/repl/initial_sync.h
@@ -46,7 +46,7 @@ namespace repl {
         /**
          * applies up to endOpTime, fetching missing documents as needed.
          */
-        void oplogApplication(OperationContext* txn, const OpTime& endOpTime);
+        void oplogApplication(OperationContext* txn, const Timestamp& endOpTime);
     };
 
     // Used for ReplSetTest testing.
diff --git a/src/mongo/db/repl/master_slave.cpp b/src/mongo/db/repl/master_slave.cpp
index b0ab3cb5037..2165b91da3d 100644
--- a/src/mongo/db/repl/master_slave.cpp
+++ b/src/mongo/db/repl/master_slave.cpp
@@ -119,8 +119,9 @@ namespace repl {
         uassert( 10119 ,  "only source='main' allowed for now with replication", sourceName() == "main" );
         BSONElement e = o.getField("syncedTo");
         if ( !e.eoo() ) {
-            uassert( 10120 ,  "bad sources 'syncedTo' field value", e.type() == Date || e.type() == Timestamp );
-            OpTime tmp( e.date() );
+            uassert(10120, "bad sources 'syncedTo' field value",
+                    e.type() == Date || e.type() == bsonTimestamp);
+            Timestamp tmp( e.date() );
             syncedTo = tmp;
         }
 
@@ -156,7 +157,7 @@ namespace repl {
         if ( !only.empty() )
             b.append("only", only);
         if ( !syncedTo.isNull() )
-            b.appendTimestamp("syncedTo", syncedTo.asDate());
+            b.append("syncedTo", syncedTo);
 
         BSONObjBuilder dbsNextPassBuilder;
         int n = 0;
@@ -453,7 +454,7 @@ namespace repl {
                 }
             }
         }
-        syncedTo = OpTime();
+        syncedTo = Timestamp();
         addDbNextPass.clear();
         save(txn);
     }
@@ -512,13 +513,13 @@ namespace repl {
     
     static DatabaseIgnorer ___databaseIgnorer;
     
-    void DatabaseIgnorer::doIgnoreUntilAfter( const string &db, const OpTime &futureOplogTime ) {
+    void DatabaseIgnorer::doIgnoreUntilAfter( const string &db, const Timestamp &futureOplogTime ) {
         if ( futureOplogTime > _ignores[ db ] ) {
             _ignores[ db ] = futureOplogTime;   
         }
     }
 
-    bool DatabaseIgnorer::ignoreAt( const string &db, const OpTime &currentOplogTime ) {
+    bool DatabaseIgnorer::ignoreAt( const string &db, const Timestamp &currentOplogTime ) {
         if ( _ignores[ db ].isNull() ) {
             return false;
         }
@@ -541,7 +542,7 @@ namespace repl {
             return true;   
         }
         BSONElement ts = op.getField( "ts" );
-        if ( ( ts.type() == Date || ts.type() == Timestamp ) && ___databaseIgnorer.ignoreAt( db, ts.date() ) ) {
+        if ( ( ts.type() == Date || ts.type() == bsonTimestamp ) && ___databaseIgnorer.ignoreAt( db, ts.date() ) ) {
             // Database is ignored due to a previous indication that it is
             // missing from master after optime "ts".
             return false;   
@@ -551,7 +552,7 @@ namespace repl {
             return true;
         }
         
-        OpTime lastTime;
+        Timestamp lastTime;
         bool dbOk = false;
         {
             // This is always a GlobalWrite lock (so no ns/db used from the context)
@@ -564,9 +565,10 @@ namespace repl {
             
             BSONObj last = oplogReader.findOne( this->ns().c_str(), Query().sort( BSON( "$natural" << -1 ) ) );
             if ( !last.isEmpty() ) {
-	            BSONElement ts = last.getField( "ts" );
-	            massert( 14032, "Invalid 'ts' in remote log", ts.type() == Date || ts.type() == Timestamp );
-	            lastTime = OpTime( ts.date() );
+                    BSONElement ts = last.getField( "ts" );
+                    massert(14032, "Invalid 'ts' in remote log",
+                            ts.type() == Date || ts.type() == bsonTimestamp);
+	            lastTime = Timestamp( ts.date() );
             }
 
             BSONObj info;
@@ -782,8 +784,9 @@ namespace repl {
         BSONObj last = oplogReader.findOne( _ns.c_str(), Query( b.done() ).sort( BSON( "$natural" << -1 ) ) );
         if ( !last.isEmpty() ) {
             BSONElement ts = last.getField( "ts" );
-            massert( 10386 ,  "non Date ts found: " + last.toString(), ts.type() == Date || ts.type() == Timestamp );
-            syncedTo = OpTime( ts.date() );
+            massert(10386, "non Date ts found: " + last.toString(),
+                    ts.type() == Date || ts.type() == bsonTimestamp);
+            syncedTo = Timestamp( ts.date() );
         }
     }
 
@@ -878,7 +881,7 @@ namespace repl {
             }
 
             BSONObjBuilder gte;
-            gte.appendTimestamp("$gte", syncedTo.asDate());
+            gte.append("$gte", syncedTo);
             BSONObjBuilder query;
             query.append("ts", gte.done());
             if ( !only.empty() ) {
@@ -931,11 +934,11 @@ namespace repl {
             return okResultCode;
         }
 
-        OpTime nextOpTime;
+        Timestamp nextOpTime;
         {
             BSONObj op = oplogReader.next();
             BSONElement ts = op.getField("ts");
-            if ( ts.type() != Date && ts.type() != Timestamp ) {
+            if ( ts.type() != Date && ts.type() != bsonTimestamp ) {
                 string err = op.getStringField("$err");
                 if ( !err.empty() ) {
                     // 13051 is "tailable cursor requested on non capped collection"
@@ -954,7 +957,7 @@ namespace repl {
                 }
             }
 
-            nextOpTime = OpTime( ts.date() );
+            nextOpTime = Timestamp( ts.date() );
             LOG(2) << "first op time received: " << nextOpTime.toString() << '\n';
             if ( initial ) {
                 LOG(1) << "initial run\n";
@@ -967,7 +970,7 @@ namespace repl {
                     verify(false);
                 }
                 oplogReader.putBack( op ); // op will be processed in the loop below
-                nextOpTime = OpTime(); // will reread the op below
+                nextOpTime = Timestamp(); // will reread the op below
             }
             else if ( nextOpTime != syncedTo ) { // didn't get what we queried for - error
                 log()
@@ -1033,15 +1036,15 @@ namespace repl {
                 while( 1 ) {
 
                     BSONElement ts = op.getField("ts");
-                    if( !( ts.type() == Date || ts.type() == Timestamp ) ) {
+                    if( !( ts.type() == Date || ts.type() == bsonTimestamp ) ) {
                         log() << "sync error: problem querying remote oplog record" << endl;
                         log() << "op: " << op.toString() << endl;
                         log() << "halting replication" << endl;
                         replInfo = replAllDead = "sync error: no ts found querying remote oplog record";
                         throw SyncException();
                     }
-                    OpTime last = nextOpTime;
-                    nextOpTime = OpTime( ts.date() );
+                    Timestamp last = nextOpTime;
+                    nextOpTime = Timestamp( ts.date() );
                     if ( !( last < nextOpTime ) ) {
                         log() << "sync error: last applied optime at slave >= nextOpTime from master" << endl;
                         log() << " last:       " << last.toStringLong() << endl;
diff --git a/src/mongo/db/repl/master_slave.h b/src/mongo/db/repl/master_slave.h
index 117e26d08a1..4a05efd48b9 100644
--- a/src/mongo/db/repl/master_slave.h
+++ b/src/mongo/db/repl/master_slave.h
@@ -135,7 +135,7 @@ namespace repl {
         std::string only; // only a certain db. note that in the sources collection, this may not be changed once you start replicating.
 
         /* the last time point we have already synced up to (in the remote/master's oplog). */
-        OpTime syncedTo;
+        Timestamp syncedTo;
 
         int nClonedThisPass;
 
@@ -176,19 +176,19 @@ namespace repl {
 
     /**
      * Helper class used to set and query an ignore state for a named database.
-     * The ignore state will expire after a specified OpTime.
+     * The ignore state will expire after a specified Timestamp.
      */
     class DatabaseIgnorer {
     public:
         /** Indicate that operations for 'db' should be ignored until after 'futureOplogTime' */
-        void doIgnoreUntilAfter( const std::string &db, const OpTime &futureOplogTime );
+        void doIgnoreUntilAfter( const std::string &db, const Timestamp &futureOplogTime );
         /**
          * Query ignore state of 'db'; if 'currentOplogTime' is after the ignore
          * limit, the ignore state will be cleared.
          */
-        bool ignoreAt( const std::string &db, const OpTime &currentOplogTime );
+        bool ignoreAt( const std::string &db, const Timestamp &currentOplogTime );
     private:
-        std::map< std::string, OpTime > _ignores;
+        std::map< std::string, Timestamp > _ignores;
     };
 
 } // namespace repl
diff --git a/src/mongo/db/repl/member_heartbeat_data.cpp b/src/mongo/db/repl/member_heartbeat_data.cpp
index 8ca22c40649..5ae8f1fbffc 100644
--- a/src/mongo/db/repl/member_heartbeat_data.cpp
+++ b/src/mongo/db/repl/member_heartbeat_data.cpp
@@ -47,8 +47,8 @@ namespace repl {
         _authIssue(false) {
 
         _lastResponse.setState(MemberState::RS_UNKNOWN);
-        _lastResponse.setElectionTime(OpTime());
-        _lastResponse.setOpTime(OpTime());
+        _lastResponse.setElectionTime(Timestamp());
+        _lastResponse.setOpTime(Timestamp());
     }
 
     void MemberHeartbeatData::setUpValues(Date_t now,
@@ -88,8 +88,8 @@ namespace repl {
 
         _lastResponse = ReplSetHeartbeatResponse();
         _lastResponse.setState(MemberState::RS_DOWN);
-        _lastResponse.setElectionTime(OpTime());
-        _lastResponse.setOpTime(OpTime());
+        _lastResponse.setElectionTime(Timestamp());
+        _lastResponse.setOpTime(Timestamp());
         _lastResponse.setHbMsg(heartbeatMessage);
         _lastResponse.setSyncingTo("");
     }
@@ -102,8 +102,8 @@ namespace repl {
 
         _lastResponse = ReplSetHeartbeatResponse();
         _lastResponse.setState(MemberState::RS_UNKNOWN);
-        _lastResponse.setElectionTime(OpTime());
-        _lastResponse.setOpTime(OpTime());
+        _lastResponse.setElectionTime(Timestamp());
+        _lastResponse.setOpTime(Timestamp());
         _lastResponse.setHbMsg("");
         _lastResponse.setSyncingTo("");
     }
diff --git a/src/mongo/db/repl/member_heartbeat_data.h b/src/mongo/db/repl/member_heartbeat_data.h
index 624c572d33f..b54c3e539d8 100644
--- a/src/mongo/db/repl/member_heartbeat_data.h
+++ b/src/mongo/db/repl/member_heartbeat_data.h
@@ -28,7 +28,7 @@
 
 #pragma once
 
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/repl/member_state.h"
 #include "mongo/db/repl/repl_set_heartbeat_response.h"
 #include "mongo/util/time_support.h"
@@ -54,11 +54,11 @@ namespace repl {
         }
         const std::string& getLastHeartbeatMsg() const { return _lastResponse.getHbMsg(); }
         const std::string& getSyncSource() const { return _lastResponse.getSyncingTo(); }
-        OpTime getOpTime() const { return _lastResponse.getOpTime(); }
+        Timestamp getOpTime() const { return _lastResponse.getOpTime(); }
         int getConfigVersion() const { return _lastResponse.getVersion(); }
         bool hasAuthIssue() const { return _authIssue; }
 
-        OpTime getElectionTime() const { return _lastResponse.getElectionTime(); }
+        Timestamp getElectionTime() const { return _lastResponse.getElectionTime(); }
 
         // Returns true if the last heartbeat data explicilty stated that the node
         // is not electable.
diff --git a/src/mongo/db/repl/minvalid.cpp b/src/mongo/db/repl/minvalid.cpp
index 5553747147a..c648dcd5fa7 100644
--- a/src/mongo/db/repl/minvalid.cpp
+++ b/src/mongo/db/repl/minvalid.cpp
@@ -32,7 +32,7 @@
 
 #include "mongo/db/repl/minvalid.h"
 
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/concurrency/d_concurrency.h"
 #include "mongo/db/dbhelpers.h"
 #include "mongo/db/jsobj.h"
@@ -63,7 +63,7 @@ namespace {
         Helpers::putSingleton(txn, minvalidNS, BSON("$set" << initialSyncFlag));
     }
 
-    void setMinValid(OperationContext* ctx, OpTime ts) {
+    void setMinValid(OperationContext* ctx, Timestamp ts) {
         ScopedTransaction transaction(ctx, MODE_IX);
         Lock::DBLock dblk(ctx->lockState(), "local", MODE_X);
         Helpers::putSingleton(ctx, minvalidNS, BSON("$set" << BSON("ts" << ts)));
@@ -84,16 +84,16 @@ namespace {
         return false;
     }
 
-    OpTime getMinValid(OperationContext* txn) {
+    Timestamp getMinValid(OperationContext* txn) {
         ScopedTransaction transaction(txn, MODE_IS);
         Lock::DBLock dblk(txn->lockState(), "local", MODE_IS);
         Lock::CollectionLock lk(txn->lockState(), minvalidNS, MODE_IS);
         BSONObj mv;
         bool found = Helpers::getSingleton(txn, minvalidNS, mv);
         if (found) {
-            return mv["ts"]._opTime();
+            return mv["ts"].timestamp();
         }
-        return OpTime();
+        return Timestamp();
     }
 
 }
diff --git a/src/mongo/db/repl/minvalid.h b/src/mongo/db/repl/minvalid.h
index 7bbe7c39c69..853c96b6c27 100644
--- a/src/mongo/db/repl/minvalid.h
+++ b/src/mongo/db/repl/minvalid.h
@@ -31,7 +31,7 @@
 namespace mongo {
     class BSONObj;
     class OperationContext;
-    class OpTime;
+    class Timestamp;
 
 namespace repl {
 
@@ -57,11 +57,11 @@ namespace repl {
     bool getInitialSyncFlag();
 
     /**
-     * The minValid optime value is the earliest (minimum) OpTime that must be applied in order to
+     * The minValid value is the earliest (minimum) Timestamp that must be applied in order to
      * consider the dataset consistent.  Do not allow client reads if our last applied operation is
      * before the minValid time.
      */
-    void setMinValid(OperationContext* ctx, OpTime ts);
-    OpTime getMinValid(OperationContext* txn);
+    void setMinValid(OperationContext* ctx, Timestamp ts);
+    Timestamp getMinValid(OperationContext* txn);
 }
 }
diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index ae387139c9a..7c90e58c8a5 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -52,7 +52,7 @@
 #include "mongo/db/dbdirectclient.h"
 #include "mongo/db/dbhelpers.h"
 #include "mongo/db/service_context.h"
-#include "mongo/db/global_optime.h"
+#include "mongo/db/global_timestamp.h"
 #include "mongo/db/index_builder.h"
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/op_observer.h"
@@ -91,7 +91,7 @@ namespace {
     Database* _localDB = nullptr;
     Collection* _localOplogCollection = nullptr;
 
-    // Synchronizes the section where a new OpTime is generated and when it actually
+    // Synchronizes the section where a new Timestamp is generated and when it actually
     // appears in the oplog.
     mongo::mutex newOpMutex;
     boost::condition newOptimeNotifier;
@@ -115,13 +115,13 @@ namespace {
      * function registers the new optime with the storage system and the replication coordinator,
      * and provides no facility to revert those registrations on rollback.
      */
-    std::pair<OpTime, long long> getNextOpTime(OperationContext* txn,
+    std::pair<Timestamp, long long> getNextOpTime(OperationContext* txn,
                                                Collection* oplog,
                                                const char* ns,
                                                ReplicationCoordinator* replCoord,
                                                const char* opstr) {
         boost::lock_guard<boost::mutex> lk(newOpMutex);
-        OpTime ts = getNextGlobalOptime();
+        Timestamp ts = getNextGlobalTimestamp();
         newOptimeNotifier.notify_all();
 
         fassert(28560, oplog->getRecordStore()->oplogDiskLocRegister(txn, ts));
@@ -151,7 +151,7 @@ namespace {
         }
 
         replCoord->setMyLastOptime(ts);
-        return std::pair<OpTime,long long>(ts, hashNew);
+        return std::pair<Timestamp,long long>(ts, hashNew);
     }
 
     /**
@@ -259,7 +259,7 @@ namespace {
                     _localOplogCollection);
         }
 
-        std::pair<OpTime, long long> slot = getNextOpTime(txn,
+        std::pair<Timestamp, long long> slot = getNextOpTime(txn,
                                                           _localOplogCollection,
                                                           ns,
                                                           replCoord,
@@ -270,7 +270,7 @@ namespace {
         */
 
         BSONObjBuilder b(256);
-        b.appendTimestamp("ts", slot.first.asDate());
+        b.append("ts", slot.first);
         b.append("h", slot.second);
         b.append("v", OPLOG_VERSION);
         b.append("op", opstr);
@@ -296,9 +296,9 @@ namespace {
         ReplClientInfo::forClient(txn->getClient()).setLastOp( slot.first );
     }
 
-    OpTime writeOpsToOplog(OperationContext* txn, const std::deque<BSONObj>& ops) {
+    Timestamp writeOpsToOplog(OperationContext* txn, const std::deque<BSONObj>& ops) {
         ReplicationCoordinator* replCoord = getGlobalReplicationCoordinator();
-        OpTime lastOptime = replCoord->getMyLastOptime();
+        Timestamp lastOptime = replCoord->getMyLastOptime();
         invariant(!ops.empty());
 
         MONGO_WRITE_CONFLICT_RETRY_LOOP_BEGIN {
@@ -323,7 +323,7 @@ namespace {
                  it != ops.end();
                  ++it) {
                 const BSONObj& op = *it;
-                const OpTime ts = op["ts"]._opTime();
+                const Timestamp ts = op["ts"].timestamp();
 
                 checkOplogInsert(_localOplogCollection->insertDocument(txn, op, false));
 
@@ -669,19 +669,19 @@ namespace {
         return Status::OK();
     }
 
-    void waitUpToOneSecondForOptimeChange(const OpTime& referenceTime) {
+    void waitUpToOneSecondForTimestampChange(const Timestamp& referenceTime) {
         boost::unique_lock<boost::mutex> lk(newOpMutex);
 
-        while (referenceTime == getLastSetOptime()) {
+        while (referenceTime == getLastSetTimestamp()) {
             if (!newOptimeNotifier.timed_wait(lk,
                                               boost::posix_time::seconds(1)))
                 return;
         }
     }
 
-    void setNewOptime(const OpTime& newTime) {
+    void setNewOptime(const Timestamp& newTime) {
         boost::lock_guard<boost::mutex> lk(newOpMutex);
-        setGlobalOptime(newTime);
+        setGlobalTimestamp(newTime);
         newOptimeNotifier.notify_all();
     }
 
diff --git a/src/mongo/db/repl/oplog.h b/src/mongo/db/repl/oplog.h
index 49e9175f0d9..f587ae074df 100644
--- a/src/mongo/db/repl/oplog.h
+++ b/src/mongo/db/repl/oplog.h
@@ -43,7 +43,7 @@ namespace mongo {
     class Database;
     class NamespaceString;
     class OperationContext;
-    class OpTime;
+    class Timestamp;
     class RecordId;
 
 namespace repl {
@@ -58,7 +58,7 @@ namespace repl {
     // used internally by replication secondaries after they have applied ops.  Updates the global
     // optime.
     // Returns the optime for the last op inserted.
-    OpTime writeOpsToOplog(OperationContext* txn,
+    Timestamp writeOpsToOplog(OperationContext* txn,
                            const std::deque<BSONObj>& ops);
 
     extern std::string rsOplogName;
@@ -104,9 +104,9 @@ namespace repl {
                                  bool convertUpdateToUpsert = false);
 
     /**
-     * Waits one second for the OpTime from the oplog to change.
+     * Waits one second for the Timestamp from the oplog to change.
      */
-    void waitUpToOneSecondForOptimeChange(const OpTime& referenceTime);
+    void waitUpToOneSecondForTimestampChange(const Timestamp& referenceTime);
 
     /**
      * Initializes the global OpTime with the value from the timestamp of the last oplog entry.
@@ -116,7 +116,7 @@ namespace repl {
     /**
      * Sets the global OpTime to be 'newTime'.
      */
-    void setNewOptime(const OpTime& newTime);
+    void setNewOptime(const Timestamp& newTime);
 
     /**
      * Detects the current replication mode and sets the "_oplogCollectionName" accordingly.
diff --git a/src/mongo/db/repl/oplogreader.cpp b/src/mongo/db/repl/oplogreader.cpp
index 9746d975fda..0301cbb0311 100644
--- a/src/mongo/db/repl/oplogreader.cpp
+++ b/src/mongo/db/repl/oplogreader.cpp
@@ -130,9 +130,9 @@ namespace repl {
         cursor.reset( _conn->query( ns, query, 0, 0, fields, _tailingQueryOptions ).release() );
     }
 
-    void OplogReader::tailingQueryGTE(const char *ns, OpTime optime, const BSONObj* fields ) {
+    void OplogReader::tailingQueryGTE(const char *ns, Timestamp optime, const BSONObj* fields ) {
         BSONObjBuilder gte;
-        gte.appendTimestamp("$gte", optime.asDate());
+        gte.append("$gte", optime);
         BSONObjBuilder query;
         query.append("ts", gte.done());
         tailingQuery(ns, query.done(), fields);
@@ -143,10 +143,10 @@ namespace repl {
     }
 
     void OplogReader::connectToSyncSource(OperationContext* txn,
-                                          OpTime lastOpTimeFetched,
+                                          Timestamp lastOpTimeFetched,
                                           ReplicationCoordinator* replCoord) {
-        const OpTime sentinel(Milliseconds(curTimeMillis64()).total_seconds(), 0);
-        OpTime oldestOpTimeSeen = sentinel;
+        const Timestamp sentinel(Milliseconds(curTimeMillis64()).total_seconds(), 0);
+        Timestamp oldestOpTimeSeen = sentinel;
 
         invariant(conn() == NULL);
 
@@ -190,7 +190,7 @@ namespace repl {
             // fetched op. Otherwise, we have fallen off the back of that source's oplog.
             BSONObj remoteOldestOp(findOne(rsOplogName.c_str(), Query()));
             BSONElement tsElem(remoteOldestOp["ts"]);
-            if (tsElem.type() != Timestamp) {
+            if (tsElem.type() != bsonTimestamp) {
                 // This member's got a bad op in its oplog.
                 warning() << "oplog invalid format on node " << candidate.toString();
                 resetConnection();
@@ -198,7 +198,7 @@ namespace repl {
                                                Date_t(curTimeMillis64() + 600*1000));
                 continue;
             }
-            OpTime remoteOldOpTime = tsElem._opTime();
+            Timestamp remoteOldOpTime = tsElem.timestamp();
 
             if (lastOpTimeFetched < remoteOldOpTime) {
                 // We're too stale to use this sync source.
diff --git a/src/mongo/db/repl/oplogreader.h b/src/mongo/db/repl/oplogreader.h
index d8639ee8530..bf089450535 100644
--- a/src/mongo/db/repl/oplogreader.h
+++ b/src/mongo/db/repl/oplogreader.h
@@ -99,10 +99,10 @@ namespace repl {
 
         void tailingQuery(const char *ns, const BSONObj& query, const BSONObj* fields=0);
 
-        void tailingQueryGTE(const char *ns, OpTime t, const BSONObj* fields=0);
+        void tailingQueryGTE(const char *ns, Timestamp t, const BSONObj* fields=0);
 
         /* Do a tailing query, but only send the ts field back. */
-        void ghostQueryGTE(const char *ns, OpTime t) {
+        void ghostQueryGTE(const char *ns, Timestamp t) {
             const BSONObj fields = BSON("ts" << 1 << "_id" << 0);
             return tailingQueryGTE(ns, t, &fields);
         }
@@ -146,7 +146,7 @@ namespace repl {
          * This function may throw DB exceptions.
          */
         void connectToSyncSource(OperationContext* txn, 
-                                 OpTime lastOpTimeFetched,
+                                 Timestamp lastOpTimeFetched,
                                  ReplicationCoordinator* replCoord);
     };
 
diff --git a/src/mongo/db/repl/optime.h b/src/mongo/db/repl/optime.h
new file mode 100644
index 00000000000..4ceee222475
--- /dev/null
+++ b/src/mongo/db/repl/optime.h
@@ -0,0 +1,83 @@
+/**
+*    Copyright (C) 2015 MongoDB Inc.
+*
+*    This program is free software: you can redistribute it and/or  modify
+*    it under the terms of the GNU Affero General Public License, version 3,
+*    as published by the Free Software Foundation.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU Affero General Public License for more details.
+*
+*    You should have received a copy of the GNU Affero General Public License
+*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*
+*    As a special exception, the copyright holders give permission to link the
+*    code of portions of this program with the OpenSSL library under certain
+*    conditions as described in each individual source file and distribute
+*    linked combinations including the program with the OpenSSL library. You
+*    must comply with the GNU Affero General Public License in all respects for
+*    all of the code used other than as permitted herein. If you modify file(s)
+*    with this exception, you may extend this exception to your version of the
+*    file(s), but you are not obligated to do so. If you do not wish to do so,
+*    delete this exception statement from your version. If you delete this
+*    exception statement from all source files in the program, then also delete
+*    it in the license file.
+*/
+
+#pragma once
+
+#include <tuple>
+#include <utility>
+
+#include "mongo/bson/timestamp.h"
+
+namespace mongo {
+namespace repl {
+
+    class OpTime {
+    public:
+        OpTime() = default;
+        OpTime(Timestamp ts, long long term) : _timestamp(std::move(ts)), _term(term) {}
+
+        Timestamp getTimestamp() const {
+            return _timestamp;
+        }
+
+        long long getTerm() const {
+            return _term;
+        }
+
+    private:
+        Timestamp _timestamp;
+        long long _term = -1;
+    };
+
+    inline bool operator==(const OpTime& lhs, const OpTime& rhs) {
+        return std::tie(lhs.opTime, lhs.term) == std::tie(rhs.opTime, rhs.term);
+    }
+
+    inline bool operator<(const OpTime& lhs, const OpTime& rhs) {
+        // Compare term first, then the opTimes.
+        return std::tie(lhs.term, lhs.opTime) < std::tie(rhs.term, rhs.opTime);
+    }
+
+    inline bool operator!=(const OpTime& lhs, const OpTime& rhs) {
+        return !(lhs == rhs);
+    }
+
+    inline bool operator<=(const OpTime& lhs, const OpTime& rhs) {
+        return lhs < rhs || lhs == rhs;
+    }
+
+    inline bool operator>(const OpTime& lhs, const OpTime& rhs) {
+        return !(lhs <= rhs);
+    }
+
+    inline bool operator>=(const OpTime& lhs, const OpTime& rhs) {
+        return !(lhs < rhs);
+    }
+
+} // namespace repl
+} // namespace mongo
diff --git a/src/mongo/db/repl/repl_client_info.h b/src/mongo/db/repl/repl_client_info.h
index 3aa0c73b66f..d7a748f8641 100644
--- a/src/mongo/db/repl/repl_client_info.h
+++ b/src/mongo/db/repl/repl_client_info.h
@@ -29,7 +29,7 @@
 #pragma once
 
 #include "mongo/bson/oid.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/client.h"
 
 namespace mongo {
@@ -43,15 +43,15 @@ namespace repl {
     public:
         static const Client::Decoration<ReplClientInfo> forClient;
 
-        void setLastOp(OpTime op) { _lastOp = op; }
-        OpTime getLastOp() const { return _lastOp; }
+        void setLastOp(Timestamp op) { _lastOp = op; }
+        Timestamp getLastOp() const { return _lastOp; }
 
         // Only used for master/slave
         void setRemoteID(OID rid) { _remoteId = rid; }
         OID getRemoteID() const { return _remoteId; }
 
     private:
-        OpTime _lastOp = OpTime();
+        Timestamp _lastOp = Timestamp();
         OID _remoteId = OID();
     };
 
diff --git a/src/mongo/db/repl/repl_set_heartbeat_response.cpp b/src/mongo/db/repl/repl_set_heartbeat_response.cpp
index 4e968ef0175..8dac175ddf9 100644
--- a/src/mongo/db/repl/repl_set_heartbeat_response.cpp
+++ b/src/mongo/db/repl/repl_set_heartbeat_response.cpp
@@ -90,13 +90,13 @@ namespace {
 
         builder->append(kOkFieldName, 1.0);
         if (_opTimeSet) {
-            builder->appendDate(kOpTimeFieldName, _opTime.asDate());
+            builder->appendDate(kOpTimeFieldName, _opTime.asULL());
         }
         if (_timeSet) {
             *builder << kTimeFieldName << _time.total_seconds();
         }
         if (_electionTimeSet) {
-            builder->appendDate(kElectionTimeFieldName, _electionTime.asDate());
+            builder->appendDate(kElectionTimeFieldName, _electionTime.asULL());
         }
         if (_configSet) {
             *builder << kConfigFieldName << _config.toBSON();
@@ -178,13 +178,13 @@ namespace {
         if (electionTimeElement.eoo()) {
             _electionTimeSet = false;
         }
-        else if (electionTimeElement.type() == Timestamp) {
+        else if (electionTimeElement.type() == bsonTimestamp) {
             _electionTimeSet = true;
-            _electionTime = electionTimeElement._opTime();
+            _electionTime = electionTimeElement.timestamp();
         }
         else if (electionTimeElement.type() == Date) {
             _electionTimeSet = true;
-            _electionTime = OpTime(electionTimeElement.date());
+            _electionTime = Timestamp(electionTimeElement.date());
         }
         else {
             return Status(ErrorCodes::TypeMismatch, str::stream() << "Expected \"" <<
@@ -212,13 +212,13 @@ namespace {
         if (opTimeElement.eoo()) {
             _opTimeSet = false;
         }
-        else if (opTimeElement.type() == Timestamp) {
+        else if (opTimeElement.type() == bsonTimestamp) {
             _opTimeSet = true;
-            _opTime = opTimeElement._opTime();
+            _opTime = opTimeElement.timestamp();
         }
         else if (opTimeElement.type() == Date) {
             _opTimeSet = true;
-            _opTime = OpTime(opTimeElement.date());
+            _opTime = Timestamp(opTimeElement.date());
         }
         else {
             return Status(ErrorCodes::TypeMismatch, str::stream() << "Expected \"" <<
@@ -329,7 +329,7 @@ namespace {
         return _state;
     }
 
-    OpTime ReplSetHeartbeatResponse::getElectionTime() const {
+    Timestamp ReplSetHeartbeatResponse::getElectionTime() const {
         invariant(_electionTimeSet);
         return _electionTime;
     }
@@ -344,7 +344,7 @@ namespace {
         return _time;
     }
 
-    OpTime ReplSetHeartbeatResponse::getOpTime() const {
+    Timestamp ReplSetHeartbeatResponse::getOpTime() const {
         invariant(_opTimeSet);
         return _opTime;
     }
diff --git a/src/mongo/db/repl/repl_set_heartbeat_response.h b/src/mongo/db/repl/repl_set_heartbeat_response.h
index a5629fbc3bf..94692d7f27c 100644
--- a/src/mongo/db/repl/repl_set_heartbeat_response.h
+++ b/src/mongo/db/repl/repl_set_heartbeat_response.h
@@ -78,14 +78,14 @@ namespace repl {
         bool hasState() const { return _stateSet; }
         MemberState getState() const;
         bool hasElectionTime() const { return _electionTimeSet; }
-        OpTime getElectionTime() const;
+        Timestamp getElectionTime() const;
         bool hasIsElectable() const { return _electableSet; }
         bool isElectable() const;
         const std::string& getHbMsg() const { return _hbmsg; }
         bool hasTime() const { return _timeSet; }
         Seconds getTime() const;
         bool hasOpTime() const { return _opTimeSet; }
-        OpTime getOpTime() const;
+        Timestamp getOpTime() const;
         const std::string& getSyncingTo() const { return _syncingTo; }
         int getVersion() const { return _version; }
         bool hasConfig() const { return _configSet; }
@@ -122,9 +122,9 @@ namespace repl {
         void setState(MemberState state) { _stateSet = true; _state = state; }
 
         /**
-         * Sets the optional "electionTime" field to the given OpTime.
+         * Sets the optional "electionTime" field to the given Timestamp.
          */
-        void setElectionTime(OpTime time) { _electionTimeSet = true; _electionTime = time; }
+        void setElectionTime(Timestamp time) { _electionTimeSet = true; _electionTime = time; }
 
         /**
          * Sets _electable to "electable" and sets _electableSet to true to indicate
@@ -147,7 +147,7 @@ namespace repl {
          * Sets _opTime to "time" and sets _opTimeSet to true to indicate that the value
          * of _opTime has been modified.
          */
-        void setOpTime(OpTime time) { _opTimeSet = true; _opTime = time; }
+        void setOpTime(Timestamp time) { _opTimeSet = true; _opTime = time; }
 
         /**
          * Sets _syncingTo to "syncingTo".
@@ -166,13 +166,13 @@ namespace repl {
 
     private:
         bool _electionTimeSet;
-        OpTime _electionTime;
+        Timestamp _electionTime;
 
         bool _timeSet;
         Seconds _time;  // Seconds since UNIX epoch.
 
         bool _opTimeSet;
-        OpTime _opTime;
+        Timestamp _opTime;
 
         bool _electableSet;
         bool _electable;
diff --git a/src/mongo/db/repl/repl_set_heartbeat_response_test.cpp b/src/mongo/db/repl/repl_set_heartbeat_response_test.cpp
index 71003ab4fec..05e634fbc03 100644
--- a/src/mongo/db/repl/repl_set_heartbeat_response_test.cpp
+++ b/src/mongo/db/repl/repl_set_heartbeat_response_test.cpp
@@ -124,7 +124,7 @@ namespace {
         ASSERT_EQUALS(hbResponseObj.toString(), hbResponseObjRoundTripChecker.toBSON().toString());
 
         // set electionTime
-        hbResponse.setElectionTime(OpTime(10,0));
+        hbResponse.setElectionTime(Timestamp(10,0));
         ++fieldsSet;
         ASSERT_EQUALS(false, hbResponse.hasState());
         ASSERT_EQUALS(true, hbResponse.hasElectionTime());
@@ -139,14 +139,14 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
 
         hbResponseObj = hbResponse.toBSON();
         ASSERT_EQUALS(fieldsSet, hbResponseObj.nFields());
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
 
         initializeResult = hbResponseObjRoundTripChecker.initialize(hbResponseObj);
         ASSERT_EQUALS(Status::OK(), initializeResult);
@@ -168,16 +168,16 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
 
         hbResponseObj = hbResponse.toBSON();
         ASSERT_EQUALS(fieldsSet, hbResponseObj.nFields());
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
 
         initializeResult = hbResponseObjRoundTripChecker.initialize(hbResponseObj);
         ASSERT_EQUALS(Status::OK(), initializeResult);
@@ -199,8 +199,8 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
 
         hbResponseObj = hbResponse.toBSON();
@@ -208,8 +208,8 @@ namespace {
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
         ASSERT_EQUALS(10, hbResponseObj["time"].numberLong());
 
         initializeResult = hbResponseObjRoundTripChecker.initialize(hbResponseObj);
@@ -232,8 +232,8 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
         ASSERT_EQUALS(true, hbResponse.isElectable());
 
@@ -242,8 +242,8 @@ namespace {
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
         ASSERT_EQUALS(10, hbResponseObj["time"].numberLong());
         ASSERT_EQUALS(true, hbResponseObj["e"].trueValue());
 
@@ -268,8 +268,8 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
@@ -279,8 +279,8 @@ namespace {
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
         ASSERT_EQUALS(10, hbResponseObj["time"].numberLong());
         ASSERT_EQUALS(true, hbResponseObj["e"].trueValue());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponseObj["config"].Obj().toString());
@@ -307,8 +307,8 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
@@ -318,8 +318,8 @@ namespace {
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
         ASSERT_EQUALS(10, hbResponseObj["time"].numberLong());
         ASSERT_EQUALS(true, hbResponseObj["e"].trueValue());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponseObj["config"].Obj().toString());
@@ -347,8 +347,8 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
@@ -358,8 +358,8 @@ namespace {
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
         ASSERT_EQUALS(10, hbResponseObj["time"].numberLong());
         ASSERT_EQUALS(true, hbResponseObj["e"].trueValue());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponseObj["config"].Obj().toString());
@@ -389,8 +389,8 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
@@ -400,8 +400,8 @@ namespace {
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
         ASSERT_EQUALS(10, hbResponseObj["time"].numberLong());
         ASSERT_EQUALS(true, hbResponseObj["e"].trueValue());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponseObj["config"].Obj().toString());
@@ -432,8 +432,8 @@ namespace {
         ASSERT_EQUALS("", hbResponse.getHbMsg());
         ASSERT_EQUALS("syncTarget", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
@@ -443,8 +443,8 @@ namespace {
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
         ASSERT_EQUALS(10, hbResponseObj["time"].numberLong());
         ASSERT_EQUALS(true, hbResponseObj["e"].trueValue());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponseObj["config"].Obj().toString());
@@ -475,8 +475,8 @@ namespace {
         ASSERT_EQUALS("lub dub", hbResponse.getHbMsg());
         ASSERT_EQUALS("syncTarget", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
@@ -486,8 +486,8 @@ namespace {
         ASSERT_EQUALS("rs0", hbResponseObj["set"].String());
         ASSERT_EQUALS("lub dub", hbResponseObj["hbmsg"].String());
         ASSERT_EQUALS(1, hbResponseObj["v"].Number());
-        ASSERT_EQUALS(OpTime(10,0), hbResponseObj["electionTime"]._opTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponseObj["opTime"]._opTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponseObj["electionTime"].timestamp());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponseObj["opTime"].timestamp());
         ASSERT_EQUALS(10, hbResponseObj["time"].numberLong());
         ASSERT_EQUALS(true, hbResponseObj["e"].trueValue());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponseObj["config"].Obj().toString());
@@ -518,8 +518,8 @@ namespace {
         ASSERT_EQUALS("lub dub", hbResponse.getHbMsg());
         ASSERT_EQUALS("syncTarget", hbResponse.getSyncingTo());
         ASSERT_EQUALS(1, hbResponse.getVersion());
-        ASSERT_EQUALS(OpTime(10,0), hbResponse.getElectionTime());
-        ASSERT_EQUALS(OpTime(0,10), hbResponse.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
         ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
@@ -724,7 +724,7 @@ namespace {
         ReplSetHeartbeatResponse hbResp;
         std::string msg = "still initializing";
         Status result = hbResp.initialize(BSON("ok" << 1.0 <<
-                                               "opTime" << OpTime()));
+                                               "opTime" << Timestamp()));
         ASSERT_EQUALS(ErrorCodes::NoSuchKey, result.code());
         ASSERT_TRUE(stringContains(result.reason(), "\"v\""))
                     << result.reason() << " doesn't contain 'v' field required error msg";
diff --git a/src/mongo/db/repl/replication_coordinator.h b/src/mongo/db/repl/replication_coordinator.h
index 06e541ac06e..934ccedb531 100644
--- a/src/mongo/db/repl/replication_coordinator.h
+++ b/src/mongo/db/repl/replication_coordinator.h
@@ -44,7 +44,7 @@ namespace mongo {
     class IndexDescriptor;
     class NamespaceString;
     class OperationContext;
-    class OpTime;
+    class Timestamp;
     struct WriteConcernOptions;
 
 namespace repl {
@@ -172,7 +172,7 @@ namespace repl {
          * ErrorCodes::Interrupted if the operation was killed with killop()
          */
         virtual StatusAndDuration awaitReplication(const OperationContext* txn,
-                                                   const OpTime& ts,
+                                                   const Timestamp& ts,
                                                    const WriteConcernOptions& writeConcern) = 0;
 
         /**
@@ -246,7 +246,7 @@ namespace repl {
          * Updates our internal tracking of the last OpTime applied for the given slave
          * identified by "rid".  Only valid to call in master/slave mode
          */
-        virtual Status setLastOptimeForSlave(const OID& rid, const OpTime& ts) = 0;
+        virtual Status setLastOptimeForSlave(const OID& rid, const Timestamp& ts) = 0;
 
         /**
          * Updates our internal tracking of the last OpTime applied to this node.
@@ -256,7 +256,7 @@ namespace repl {
          * that after calls to resetLastOpTimeFromOplog(), the minimum acceptable value for "ts" is
          * reset based on the contents of the oplog, and may go backwards due to rollback.
          */
-        virtual void setMyLastOptime(const OpTime& ts) = 0;
+        virtual void setMyLastOptime(const Timestamp& ts) = 0;
 
         /**
          * Same as above, but used during places we need to zero our last optime.
@@ -271,7 +271,7 @@ namespace repl {
         /**
          * Returns the last optime recorded by setMyLastOptime.
          */
-        virtual OpTime getMyLastOptime() const = 0;
+        virtual Timestamp getMyLastOptime() const = 0;
 
         /**
          * Retrieves and returns the current election id, which is a unique id that is local to
@@ -443,7 +443,7 @@ namespace repl {
             HostAndPort who;  // host and port of the member that sent the replSetFresh command
             unsigned id;  // replSet id of the member that sent the replSetFresh command
             int cfgver;  // replSet config version that the member who sent the command thinks it has
-            OpTime opTime;  // last optime seen by the member who sent the replSetFresh command
+            Timestamp opTime;  // last optime seen by the member who sent the replSetFresh command
         };
 
         /*
@@ -503,7 +503,7 @@ namespace repl {
         /**
          * Returns a vector of members that have applied the operation with OpTime 'op'.
          */
-        virtual std::vector<HostAndPort> getHostsWrittenTo(const OpTime& op) = 0;
+        virtual std::vector<HostAndPort> getHostsWrittenTo(const Timestamp& op) = 0;
 
         /**
          * Returns a vector of the members other than ourself in the replica set, as specified in
@@ -554,7 +554,7 @@ namespace repl {
          * Committed means a majority of the voting nodes of the config are known to have the
          * operation in their oplogs.  This implies such ops will never be rolled back.
          */
-        virtual OpTime getLastCommittedOpTime() const = 0;
+        virtual Timestamp getLastCommittedOpTime() const = 0;
 
     protected:
 
diff --git a/src/mongo/db/repl/replication_coordinator_external_state.h b/src/mongo/db/repl/replication_coordinator_external_state.h
index 7734d119040..07fa9ed921a 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state.h
+++ b/src/mongo/db/repl/replication_coordinator_external_state.h
@@ -31,7 +31,7 @@
 #include <boost/scoped_ptr.hpp>
 
 #include "mongo/base/disallow_copying.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/util/time_support.h"
 
 namespace mongo {
@@ -114,13 +114,13 @@ namespace repl {
         /**
          * Sets the global opTime to be 'newTime'.
          */
-        virtual void setGlobalOpTime(const OpTime& newTime) = 0;
+        virtual void setGlobalTimestamp(const Timestamp& newTime) = 0;
 
         /**
          * Gets the last optime of an operation performed on this host, from stable
          * storage.
          */
-        virtual StatusWith<OpTime> loadLastOpTime(OperationContext* txn) = 0;
+        virtual StatusWith<Timestamp> loadLastOpTime(OperationContext* txn) = 0;
 
         /**
          * Returns the HostAndPort of the remote client connected to us that initiated the operation
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp b/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
index 824aac77634..6a83bba6d50 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
@@ -186,38 +186,38 @@ namespace {
         }
     }
 
-    void ReplicationCoordinatorExternalStateImpl::setGlobalOpTime(const OpTime& newTime) {
+    void ReplicationCoordinatorExternalStateImpl::setGlobalTimestamp(const Timestamp& newTime) {
         setNewOptime(newTime);
     }
 
-    StatusWith<OpTime> ReplicationCoordinatorExternalStateImpl::loadLastOpTime(
+    StatusWith<Timestamp> ReplicationCoordinatorExternalStateImpl::loadLastOpTime(
             OperationContext* txn) {
 
         try {
             BSONObj oplogEntry;
             if (!Helpers::getLast(txn, rsOplogName.c_str(), oplogEntry)) {
-                return StatusWith<OpTime>(
+                return StatusWith<Timestamp>(
                         ErrorCodes::NoMatchingDocument,
                         str::stream() << "Did not find any entries in " << rsOplogName);
             }
             BSONElement tsElement = oplogEntry[tsFieldName];
             if (tsElement.eoo()) {
-                return StatusWith<OpTime>(
+                return StatusWith<Timestamp>(
                         ErrorCodes::NoSuchKey,
                         str::stream() << "Most recent entry in " << rsOplogName << " missing \"" <<
                         tsFieldName << "\" field");
             }
-            if (tsElement.type() != Timestamp) {
-                return StatusWith<OpTime>(
+            if (tsElement.type() != bsonTimestamp) {
+                return StatusWith<Timestamp>(
                         ErrorCodes::TypeMismatch,
                         str::stream() << "Expected type of \"" << tsFieldName <<
                         "\" in most recent " << rsOplogName <<
                         " entry to have type Timestamp, but found " << typeName(tsElement.type()));
             }
-            return StatusWith<OpTime>(tsElement._opTime());
+            return StatusWith<Timestamp>(tsElement.timestamp());
         }
         catch (const DBException& ex) {
-            return StatusWith<OpTime>(ex.toStatus());
+            return StatusWith<Timestamp>(ex.toStatus());
         }
     }
 
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_impl.h b/src/mongo/db/repl/replication_coordinator_external_state_impl.h
index 3d1c7bef733..482b143f629 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_impl.h
+++ b/src/mongo/db/repl/replication_coordinator_external_state_impl.h
@@ -54,8 +54,8 @@ namespace repl {
         virtual bool isSelf(const HostAndPort& host);
         virtual StatusWith<BSONObj> loadLocalConfigDocument(OperationContext* txn);
         virtual Status storeLocalConfigDocument(OperationContext* txn, const BSONObj& config);
-        virtual void setGlobalOpTime(const OpTime& newTime);
-        virtual StatusWith<OpTime> loadLastOpTime(OperationContext* txn);
+        virtual void setGlobalTimestamp(const Timestamp& newTime);
+        virtual StatusWith<Timestamp> loadLastOpTime(OperationContext* txn);
         virtual HostAndPort getClientHostAndPort(const OperationContext* txn);
         virtual void closeConnections();
         virtual void killAllUserOperations(OperationContext* txn);
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_mock.cpp b/src/mongo/db/repl/replication_coordinator_external_state_mock.cpp
index e308bc2588e..bd4e194c5fc 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_mock.cpp
+++ b/src/mongo/db/repl/replication_coordinator_external_state_mock.cpp
@@ -108,16 +108,16 @@ namespace repl {
         _localRsConfigDocument = localConfigDocument;
     }
 
-    void ReplicationCoordinatorExternalStateMock::setGlobalOpTime(const OpTime& newTime) {
+    void ReplicationCoordinatorExternalStateMock::setGlobalTimestamp(const Timestamp& newTime) {
     }
 
-    StatusWith<OpTime> ReplicationCoordinatorExternalStateMock::loadLastOpTime(
+    StatusWith<Timestamp> ReplicationCoordinatorExternalStateMock::loadLastOpTime(
         OperationContext* txn) {
         return _lastOpTime;
     }
 
     void ReplicationCoordinatorExternalStateMock::setLastOpTime(
-        const StatusWith<OpTime>& lastApplied) {
+        const StatusWith<Timestamp>& lastApplied) {
         _lastOpTime = lastApplied;
     }
 
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_mock.h b/src/mongo/db/repl/replication_coordinator_external_state_mock.h
index 2f86ebc4d77..8f4366b7e17 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_mock.h
+++ b/src/mongo/db/repl/replication_coordinator_external_state_mock.h
@@ -28,12 +28,14 @@
 
 #pragma once
 
+#include <boost/thread.hpp>
+#include <boost/thread/condition.hpp>
 #include <vector>
 
 #include "mongo/base/disallow_copying.h"
 #include "mongo/base/status_with.h"
 #include "mongo/bson/oid.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/repl/replication_coordinator_external_state.h"
 #include "mongo/util/net/hostandport.h"
@@ -58,8 +60,8 @@ namespace repl {
         virtual HostAndPort getClientHostAndPort(const OperationContext* txn);
         virtual StatusWith<BSONObj> loadLocalConfigDocument(OperationContext* txn);
         virtual Status storeLocalConfigDocument(OperationContext* txn, const BSONObj& config);
-        virtual void setGlobalOpTime(const OpTime& newTime);
-        virtual StatusWith<OpTime> loadLastOpTime(OperationContext* txn);
+        virtual void setGlobalTimestamp(const Timestamp& newTime);
+        virtual StatusWith<Timestamp> loadLastOpTime(OperationContext* txn);
         virtual void closeConnections();
         virtual void killAllUserOperations(OperationContext* txn);
         virtual void clearShardingState();
@@ -86,7 +88,7 @@ namespace repl {
         /**
          * Sets the return value for subsequent calls to loadLastOpTimeApplied.
          */
-        void setLastOpTime(const StatusWith<OpTime>& lastApplied);
+        void setLastOpTime(const StatusWith<Timestamp>& lastApplied);
 
         /**
          * Sets the return value for subsequent calls to storeLocalConfigDocument().
@@ -102,7 +104,7 @@ namespace repl {
 
     private:
         StatusWith<BSONObj> _localRsConfigDocument;
-        StatusWith<OpTime>  _lastOpTime;
+        StatusWith<Timestamp>  _lastOpTime;
         std::vector<HostAndPort> _selfHosts;
         bool _canAcquireGlobalSharedLock;
         Status _storeLocalConfigDocumentStatus;
diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index 3ee5b1227ea..4f9e9514509 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -37,7 +37,7 @@
 
 #include "mongo/base/status.h"
 #include "mongo/db/concurrency/d_concurrency.h"
-#include "mongo/db/global_optime.h"
+#include "mongo/db/global_timestamp.h"
 #include "mongo/db/index/index_descriptor.h"
 #include "mongo/db/operation_context_noop.h"
 #include "mongo/db/repl/check_quorum_for_config_change.h"
@@ -109,7 +109,7 @@ namespace {
          */
         WaiterInfo(std::vector<WaiterInfo*>* _list,
                    unsigned int _opID,
-                   const OpTime* _opTime,
+                   const Timestamp* _opTime,
                    const WriteConcernOptions* _writeConcern,
                    boost::condition_variable* _condVar) : list(_list),
                                                           master(true),
@@ -127,7 +127,7 @@ namespace {
         std::vector<WaiterInfo*>* list;
         bool master; // Set to false to indicate that stepDown was called while waiting
         const unsigned int opID;
-        const OpTime* opTime;
+        const Timestamp* opTime;
         const WriteConcernOptions* writeConcern;
         boost::condition_variable* condVar;
     };
@@ -213,7 +213,7 @@ namespace {
             fassertFailedNoTrace(28545);
         }
 
-        StatusWith<OpTime> lastOpTimeStatus = _externalState->loadLastOpTime(txn);
+        StatusWith<Timestamp> lastOpTimeStatus = _externalState->loadLastOpTime(txn);
 
         // Use a callback here, because _finishLoadLocalConfig calls isself() which requires
         // that the server's networking layer be up and running and accepting connections, which
@@ -230,7 +230,7 @@ namespace {
     void ReplicationCoordinatorImpl::_finishLoadLocalConfig(
             const ReplicationExecutor::CallbackData& cbData,
             const ReplicaSetConfig& localConfig,
-            const StatusWith<OpTime>& lastOpTimeStatus) {
+            const StatusWith<Timestamp>& lastOpTimeStatus) {
         if (!cbData.status.isOK()) {
             LOG(1) << "Loading local replica set configuration failed due to " << cbData.status;
             return;
@@ -266,7 +266,7 @@ namespace {
         // Do not check optime, if this node is an arbiter.
         bool isArbiter = myIndex.getValue() != -1 &&
             localConfig.getMemberAt(myIndex.getValue()).isArbiter();
-        OpTime lastOpTime(0, 0);
+        Timestamp lastOpTime(0, 0);
         if (!isArbiter) {
             if (!lastOpTimeStatus.isOK()) {
                 warning() << "Failed to load timestamp of most recently applied operation; " <<
@@ -282,7 +282,7 @@ namespace {
         const PostMemberStateUpdateAction action =
             _setCurrentRSConfig_inlock(localConfig, myIndex.getValue());
         _setMyLastOptime_inlock(&lk, lastOpTime, false);
-        _externalState->setGlobalOpTime(lastOpTime);
+        _externalState->setGlobalTimestamp(lastOpTime);
         if (lk.owns_lock()) {
             lk.unlock();
         }
@@ -575,7 +575,7 @@ namespace {
     }
 
     void ReplicationCoordinatorImpl::_updateSlaveInfoOptime_inlock(SlaveInfo* slaveInfo,
-                                                                   OpTime ts) {
+                                                                   Timestamp ts) {
 
         slaveInfo->opTime = ts;
 
@@ -646,7 +646,7 @@ namespace {
     }
 
     Status ReplicationCoordinatorImpl::setLastOptimeForSlave(const OID& rid,
-                                                             const OpTime& ts) {
+                                                             const Timestamp& ts) {
         boost::unique_lock<boost::mutex> lock(_mutex);
         massert(28576,
                 "Received an old style replication progress update, which is only used for Master/"
@@ -682,18 +682,18 @@ namespace {
         _replExecutor.wait(cbh.getValue());
     }
 
-    void ReplicationCoordinatorImpl::setMyLastOptime(const OpTime& ts) {
+    void ReplicationCoordinatorImpl::setMyLastOptime(const Timestamp& ts) {
         boost::unique_lock<boost::mutex> lock(_mutex);
         _setMyLastOptime_inlock(&lock, ts, false);
     }
 
     void ReplicationCoordinatorImpl::resetMyLastOptime() {
         boost::unique_lock<boost::mutex> lock(_mutex);
-        _setMyLastOptime_inlock(&lock, OpTime(), true);
+        _setMyLastOptime_inlock(&lock, Timestamp(), true);
     }
 
     void ReplicationCoordinatorImpl::_setMyLastOptime_inlock(
-            boost::unique_lock<boost::mutex>* lock, const OpTime& ts, bool isRollbackAllowed) {
+            boost::unique_lock<boost::mutex>* lock, const Timestamp& ts, bool isRollbackAllowed) {
         invariant(lock->owns_lock());
         SlaveInfo* mySlaveInfo = &_slaveInfo[_getMyIndexInSlaveInfo_inlock()];
         invariant(isRollbackAllowed || mySlaveInfo->opTime <= ts);
@@ -709,18 +709,18 @@ namespace {
         _externalState->forwardSlaveProgress(); // Must do this outside _mutex
     }
 
-    OpTime ReplicationCoordinatorImpl::getMyLastOptime() const {
+    Timestamp ReplicationCoordinatorImpl::getMyLastOptime() const {
         boost::lock_guard<boost::mutex> lock(_mutex);
         return _getMyLastOptime_inlock();
     }
 
-    OpTime ReplicationCoordinatorImpl::_getMyLastOptime_inlock() const {
+    Timestamp ReplicationCoordinatorImpl::_getMyLastOptime_inlock() const {
         return _slaveInfo[_getMyIndexInSlaveInfo_inlock()].opTime;
     }
 
     Status ReplicationCoordinatorImpl::setLastOptime_forTest(long long cfgVer,
                                                              long long memberId,
-                                                             const OpTime& ts) {
+                                                             const Timestamp& ts) {
         boost::lock_guard<boost::mutex> lock(_mutex);
         invariant(_getReplicationMode_inlock() == modeReplSet);
 
@@ -824,7 +824,7 @@ namespace {
     }
 
     bool ReplicationCoordinatorImpl::_doneWaitingForReplication_inlock(
-        const OpTime& opTime, const WriteConcernOptions& writeConcern) {
+        const Timestamp& opTime, const WriteConcernOptions& writeConcern) {
         Status status = _checkIfWriteConcernCanBeSatisfied_inlock(writeConcern);
         if (!status.isOK()) {
             return true;
@@ -850,7 +850,7 @@ namespace {
         }
     }
 
-    bool ReplicationCoordinatorImpl::_haveNumNodesReachedOpTime_inlock(const OpTime& opTime, 
+    bool ReplicationCoordinatorImpl::_haveNumNodesReachedOpTime_inlock(const Timestamp& opTime, 
                                                                        int numNodes) {
         if (_getMyLastOptime_inlock() < opTime) {
             // Secondaries that are for some reason ahead of us should not allow us to
@@ -861,7 +861,7 @@ namespace {
         for (SlaveInfoVector::iterator it = _slaveInfo.begin();
                 it != _slaveInfo.end(); ++it) {
 
-            const OpTime& slaveTime = it->opTime;
+            const Timestamp& slaveTime = it->opTime;
             if (slaveTime >= opTime) {
                 --numNodes;
             }
@@ -874,13 +874,13 @@ namespace {
     }
 
     bool ReplicationCoordinatorImpl::_haveTaggedNodesReachedOpTime_inlock(
-        const OpTime& opTime, const ReplicaSetTagPattern& tagPattern) {
+        const Timestamp& opTime, const ReplicaSetTagPattern& tagPattern) {
 
         ReplicaSetTagMatch matcher(tagPattern);
         for (SlaveInfoVector::iterator it = _slaveInfo.begin();
                 it != _slaveInfo.end(); ++it) {
 
-            const OpTime& slaveTime = it->opTime;
+            const Timestamp& slaveTime = it->opTime;
             if (slaveTime >= opTime) {
                 // This node has reached the desired optime, now we need to check if it is a part
                 // of the tagPattern.
@@ -899,7 +899,7 @@ namespace {
 
     ReplicationCoordinator::StatusAndDuration ReplicationCoordinatorImpl::awaitReplication(
             const OperationContext* txn,
-            const OpTime& opTime,
+            const Timestamp& opTime,
             const WriteConcernOptions& writeConcern) {
         Timer timer;
         boost::unique_lock<boost::mutex> lock(_mutex);
@@ -924,7 +924,7 @@ namespace {
             const Timer* timer,
             boost::unique_lock<boost::mutex>* lock,
             const OperationContext* txn,
-            const OpTime& opTime,
+            const Timestamp& opTime,
             const WriteConcernOptions& writeConcern) {
 
         const Mode replMode = _getReplicationMode_inlock();
@@ -1951,7 +1951,7 @@ namespace {
         case kActionWinElection: {
             boost::unique_lock<boost::mutex> lk(_mutex);
             _electionId = OID::gen();
-            _topCoord->processWinElection(_electionId, getNextGlobalOptime());
+            _topCoord->processWinElection(_electionId, getNextGlobalTimestamp());
             _isWaitingForDrainToComplete = true;
             const PostMemberStateUpdateAction nextAction =
                 _updateMemberStateFromTopologyCoordinator_inlock();
@@ -2049,7 +2049,7 @@ namespace {
          invariant(_settings.usingReplSets());
          _cancelHeartbeats();
          _setConfigState_inlock(kConfigSteady);
-         OpTime myOptime = _getMyLastOptime_inlock(); // Must get this before changing our config.
+         Timestamp myOptime = _getMyLastOptime_inlock(); // Must get this before changing our config.
          _topCoord->updateConfig(
                  newConfig,
                  myIndex,
@@ -2146,7 +2146,7 @@ namespace {
         return self.shouldBuildIndexes();
     }
 
-    std::vector<HostAndPort> ReplicationCoordinatorImpl::getHostsWrittenTo(const OpTime& op) {
+    std::vector<HostAndPort> ReplicationCoordinatorImpl::getHostsWrittenTo(const Timestamp& op) {
         std::vector<HostAndPort> hosts;
         boost::lock_guard<boost::mutex> lk(_mutex);
         for (size_t i = 0; i < _slaveInfo.size(); ++i) {
@@ -2305,8 +2305,8 @@ namespace {
     }
 
     void ReplicationCoordinatorImpl::resetLastOpTimeFromOplog(OperationContext* txn) {
-        StatusWith<OpTime> lastOpTimeStatus = _externalState->loadLastOpTime(txn);
-        OpTime lastOpTime(0, 0);
+        StatusWith<Timestamp> lastOpTimeStatus = _externalState->loadLastOpTime(txn);
+        Timestamp lastOpTime(0, 0);
         if (!lastOpTimeStatus.isOK()) {
             warning() << "Failed to load timestamp of most recently applied operation; " <<
                 lastOpTimeStatus.getStatus();
@@ -2316,7 +2316,7 @@ namespace {
         }
         boost::unique_lock<boost::mutex> lk(_mutex);
         _setMyLastOptime_inlock(&lk, lastOpTime, true);
-        _externalState->setGlobalOpTime(lastOpTime);
+        _externalState->setGlobalTimestamp(lastOpTime);
     }
 
     void ReplicationCoordinatorImpl::_shouldChangeSyncSource(
@@ -2355,7 +2355,7 @@ namespace {
         invariant(tagPattern.isOK());
         ReplicaSetTagMatch matcher{tagPattern.getValue()};
 
-        std::vector<OpTime> votingNodesOpTimes;
+        std::vector<Timestamp> votingNodesOpTimes;
 
         for (const auto& sI : _slaveInfo) {
             auto memberConfig = _rsConfig.findMemberByID(sI.memberId);
@@ -2375,7 +2375,7 @@ namespace {
         _lastCommittedOpTime = votingNodesOpTimes[(votingNodesOpTimes.size() - 1) / 2];
     }
 
-    OpTime ReplicationCoordinatorImpl::getLastCommittedOpTime() const {
+    Timestamp ReplicationCoordinatorImpl::getLastCommittedOpTime() const {
         boost::unique_lock<boost::mutex> lk(_mutex);
         return _lastCommittedOpTime;
     }
diff --git a/src/mongo/db/repl/replication_coordinator_impl.h b/src/mongo/db/repl/replication_coordinator_impl.h
index a66043ac23e..970d6c877f1 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.h
+++ b/src/mongo/db/repl/replication_coordinator_impl.h
@@ -35,7 +35,7 @@
 #include <vector>
 
 #include "mongo/base/status.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/service_context.h"
 #include "mongo/db/repl/member_state.h"
 #include "mongo/db/repl/replica_set_config.h"
@@ -110,7 +110,7 @@ namespace repl {
 
         virtual ReplicationCoordinator::StatusAndDuration awaitReplication(
                 const OperationContext* txn,
-                const OpTime& ts,
+                const Timestamp& ts,
                 const WriteConcernOptions& writeConcern);
 
         virtual ReplicationCoordinator::StatusAndDuration awaitReplicationOfLastOpForClient(
@@ -135,15 +135,15 @@ namespace repl {
 
         virtual bool shouldIgnoreUniqueIndex(const IndexDescriptor* idx);
 
-        virtual Status setLastOptimeForSlave(const OID& rid, const OpTime& ts);
+        virtual Status setLastOptimeForSlave(const OID& rid, const Timestamp& ts);
 
-        virtual void setMyLastOptime(const OpTime& ts);
+        virtual void setMyLastOptime(const Timestamp& ts);
 
         virtual void resetMyLastOptime();
 
         virtual void setMyHeartbeatMessage(const std::string& msg);
 
-        virtual OpTime getMyLastOptime() const;
+        virtual Timestamp getMyLastOptime() const;
 
         virtual OID getElectionId();
 
@@ -208,7 +208,7 @@ namespace repl {
 
         virtual bool buildsIndexes();
 
-        virtual std::vector<HostAndPort> getHostsWrittenTo(const OpTime& op);
+        virtual std::vector<HostAndPort> getHostsWrittenTo(const Timestamp& op);
 
         virtual std::vector<HostAndPort> getOtherNodesInReplSet() const;
 
@@ -226,7 +226,7 @@ namespace repl {
 
         virtual bool shouldChangeSyncSource(const HostAndPort& currentSource);
 
-        virtual OpTime getLastCommittedOpTime() const;
+        virtual Timestamp getLastCommittedOpTime() const;
 
 
         // ================== Test support API ===================
@@ -245,7 +245,7 @@ namespace repl {
         /**
          * Simple wrapper around _setLastOptime_inlock to make it easier to test.
          */
-        Status setLastOptime_forTest(long long cfgVer, long long memberId, const OpTime& ts);
+        Status setLastOptime_forTest(long long cfgVer, long long memberId, const Timestamp& ts);
 
     private:
 
@@ -296,7 +296,7 @@ namespace repl {
         // Struct that holds information about nodes in this replication group, mainly used for
         // tracking replication progress for write concern satisfaction.
         struct SlaveInfo {
-            OpTime opTime; // Our last known OpTime that this slave has replicated to.
+            Timestamp opTime; // Our last known OpTime that this slave has replicated to.
             HostAndPort hostAndPort; // Client address of the slave.
             int memberId; // Id of the node in the replica set config, or -1 if we're not a replSet.
             OID rid; // RID of the node.
@@ -331,7 +331,7 @@ namespace repl {
          * and wakes up any threads waiting for replication that now have their write concern
          * satisfied.
          */
-        void _updateSlaveInfoOptime_inlock(SlaveInfo* slaveInfo, OpTime ts);
+        void _updateSlaveInfoOptime_inlock(SlaveInfo* slaveInfo, Timestamp ts);
 
         /**
          * Returns the index into _slaveInfo where data corresponding to ourself is stored.
@@ -430,25 +430,25 @@ namespace repl {
                 const Timer* timer,
                 boost::unique_lock<boost::mutex>* lock,
                 const OperationContext* txn,
-                const OpTime& ts,
+                const Timestamp& ts,
                 const WriteConcernOptions& writeConcern);
 
         /*
          * Returns true if the given writeConcern is satisfied up to "optime" or is unsatisfiable.
          */
-        bool _doneWaitingForReplication_inlock(const OpTime& opTime,
+        bool _doneWaitingForReplication_inlock(const Timestamp& opTime,
                                                const WriteConcernOptions& writeConcern);
 
         /**
          * Helper for _doneWaitingForReplication_inlock that takes an integer write concern.
          */
-        bool _haveNumNodesReachedOpTime_inlock(const OpTime& opTime, int numNodes);
+        bool _haveNumNodesReachedOpTime_inlock(const Timestamp& opTime, int numNodes);
 
         /**
          * Helper for _doneWaitingForReplication_inlock that takes a tag pattern representing a
          * named write concern mode.
          */
-        bool _haveTaggedNodesReachedOpTime_inlock(const OpTime& opTime,
+        bool _haveTaggedNodesReachedOpTime_inlock(const Timestamp& opTime,
                                                   const ReplicaSetTagPattern& tagPattern);
 
         Status _checkIfWriteConcernCanBeSatisfied_inlock(
@@ -479,7 +479,7 @@ namespace repl {
 
         int _getMyId_inlock() const;
 
-        OpTime _getMyLastOptime_inlock() const;
+        Timestamp _getMyLastOptime_inlock() const;
 
 
         /**
@@ -514,7 +514,7 @@ namespace repl {
          * "isRollbackAllowed" is true.
          */
         void _setMyLastOptime_inlock(boost::unique_lock<boost::mutex>* lock,
-                                     const OpTime& ts,
+                                     const Timestamp& ts,
                                      bool isRollbackAllowed);
 
         /**
@@ -541,7 +541,7 @@ namespace repl {
          *
          * Updates the optime associated with the member at "memberIndex" in our config.
          */
-        void _updateOpTimeFromHeartbeat_inlock(int memberIndex, OpTime optime);
+        void _updateOpTimeFromHeartbeat_inlock(int memberIndex, Timestamp optime);
 
         /**
          * Starts a heartbeat for each member in the current config.  Called within the executor
@@ -591,7 +591,7 @@ namespace repl {
          */
         void _finishLoadLocalConfig(const ReplicationExecutor::CallbackData& cbData,
                                     const ReplicaSetConfig& localConfig,
-                                    const StatusWith<OpTime>& lastOpTimeStatus);
+                                    const StatusWith<Timestamp>& lastOpTimeStatus);
 
         /**
          * Callback that finishes the work of processReplSetInitiate() inside the replication
@@ -888,7 +888,7 @@ namespace repl {
         AtomicUInt32 _canServeNonLocalReads;                                              // (S)
 
         // OpTime of the latest committed operation. Matches the concurrency level of _slaveInfo.
-        OpTime _lastCommittedOpTime;                                                          // (M)
+        Timestamp _lastCommittedOpTime;                                                          // (M)
     };
 
 } // namespace repl
diff --git a/src/mongo/db/repl/replication_coordinator_impl_elect.cpp b/src/mongo/db/repl/replication_coordinator_impl_elect.cpp
index 57d150b8e48..dffe1e3793f 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_elect.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_elect.cpp
@@ -120,9 +120,9 @@ namespace {
 
 
         invariant(_rsConfig.getMemberAt(_selfIndex).isElectable());
-        OpTime lastOpTimeApplied(_getMyLastOptime_inlock());
+        Timestamp lastOpTimeApplied(_getMyLastOptime_inlock());
 
-        if (lastOpTimeApplied == OpTime()) {
+        if (lastOpTimeApplied == Timestamp()) {
             log() << "not trying to elect self, "
                 "do not yet have a complete set of data from any point in time";
             return;
diff --git a/src/mongo/db/repl/replication_coordinator_impl_elect_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_elect_test.cpp
index b7674970363..5ea30666316 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_elect_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_elect_test.cpp
@@ -99,7 +99,7 @@ namespace {
                 net->scheduleResponse(noi, net->now(), makeResponseStatus(
                                               BSON("ok" << 1 <<
                                                    "fresher" << false <<
-                                                   "opTime" << Date_t(OpTime(0, 0).asDate()) <<
+                                                   "opTime" << Date_t(Timestamp(0, 0).asULL()) <<
                                                    "veto" << false)));
             }
             else {
@@ -149,7 +149,7 @@ namespace {
         ASSERT(getReplCoord()->getMemberState().secondary()) <<
                                                       getReplCoord()->getMemberState().toString();
 
-        getReplCoord()->setMyLastOptime(OpTime(10,0));
+        getReplCoord()->setMyLastOptime(Timestamp(10,0));
 
         NetworkInterfaceMock* net = getNet();
         net->enterNetwork();
@@ -210,7 +210,7 @@ namespace {
                                 ));
         assertStartSuccess(configObj, HostAndPort("node1", 12345));
         OperationContextNoop txn;
-        getReplCoord()->setMyLastOptime(OpTime (100, 1));
+        getReplCoord()->setMyLastOptime(Timestamp (100, 1));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
         startCapturingLogMessages();
         simulateSuccessfulElection();
@@ -231,7 +231,7 @@ namespace {
         ReplicaSetConfig config = assertMakeRSConfig(configObj);
 
         OperationContextNoop txn;
-        OpTime time1(100, 1);
+        Timestamp time1(100, 1);
         getReplCoord()->setMyLastOptime(time1);
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
 
@@ -278,7 +278,7 @@ namespace {
         ReplicaSetConfig config = assertMakeRSConfig(configObj);
 
         OperationContextNoop txn;
-        OpTime time1(100, 1);
+        Timestamp time1(100, 1);
         getReplCoord()->setMyLastOptime(time1);
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
 
@@ -326,7 +326,7 @@ namespace {
                                          BSON("_id" << 5 << "host" << "node5:12345") )),
             HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100,0));
+        getReplCoord()->setMyLastOptime(Timestamp(100,0));
 
         // set hbreconfig to hang while in progress
         getExternalState()->setStoreLocalConfigDocumentToHang(true);
diff --git a/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp b/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
index 9ec647d8dee..ab278b5c7b7 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
@@ -126,7 +126,7 @@ namespace {
         const bool isUnauthorized = (responseStatus.code() == ErrorCodes::Unauthorized) ||
                                     (responseStatus.code() == ErrorCodes::AuthenticationFailed);
         const Date_t now = _replExecutor.now();
-        const OpTime lastApplied = getMyLastOptime();  // Locks and unlocks _mutex.
+        const Timestamp lastApplied = getMyLastOptime();  // Locks and unlocks _mutex.
         Milliseconds networkTime(0);
         StatusWith<ReplSetHeartbeatResponse> hbStatusResponse(hbResponse);
 
@@ -177,7 +177,7 @@ namespace {
     }
 
     void ReplicationCoordinatorImpl::_updateOpTimeFromHeartbeat_inlock(int targetIndex,
-                                                                       OpTime optime) {
+                                                                       Timestamp optime) {
         invariant(_selfIndex >= 0);
         invariant(targetIndex >= 0);
 
diff --git a/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp
index 7b1b8f8ff20..f29a830bb6f 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp
@@ -92,7 +92,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         BSONObjBuilder result;
@@ -123,7 +123,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         BSONObjBuilder result;
@@ -151,7 +151,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         BSONObjBuilder result;
@@ -207,7 +207,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         Status status(ErrorCodes::InternalError, "Not Set");
@@ -243,7 +243,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         Status status(ErrorCodes::InternalError, "Not Set");
@@ -281,7 +281,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         Status status(ErrorCodes::InternalError, "Not Set");
@@ -316,7 +316,7 @@ namespace {
         init();
         start(HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
 
         // initiate
         Status status(ErrorCodes::InternalError, "Not Set");
@@ -354,7 +354,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345"))),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         Status status(ErrorCodes::InternalError, "Not Set");
@@ -391,7 +391,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100,0));
+        getReplCoord()->setMyLastOptime(Timestamp(100,0));
         simulateSuccessfulElection();
         ASSERT_TRUE(getReplCoord()->getMemberState().primary());
 
@@ -443,7 +443,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100,0));
+        getReplCoord()->setMyLastOptime(Timestamp(100,0));
         simulateSuccessfulElection();
         ASSERT_TRUE(getReplCoord()->getMemberState().primary());
  
@@ -502,7 +502,7 @@ namespace {
                                                  BSON("_id" << 2 << "host" << "node2:12345") )),
                     HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
 
         // fail before forced
         BSONObjBuilder result;
diff --git a/src/mongo/db/repl/replication_coordinator_impl_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
index 550ef262f62..d7fcffc6ed6 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
@@ -406,7 +406,7 @@ namespace {
     TEST_F(ReplCoordTest, AwaitReplicationNoReplEnabled) {
         init("");
         OperationContextNoop txn;
-        OpTime time(100, 1);
+        Timestamp time(100, 1);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = WriteConcernOptions::kNoWaiting;
@@ -424,7 +424,7 @@ namespace {
         settings.master = true;
         init(settings);
         OperationContextNoop txn;
-        OpTime time(100, 1);
+        Timestamp time(100, 1);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = WriteConcernOptions::kNoWaiting;
@@ -449,7 +449,7 @@ namespace {
                 HostAndPort("node1", 12345));
 
         OperationContextNoop txn;
-        OpTime time(100, 1);
+        Timestamp time(100, 1);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = WriteConcernOptions::kNoWaiting;
@@ -462,7 +462,7 @@ namespace {
         ASSERT_EQUALS(ErrorCodes::NotMaster, statusAndDur.status);
 
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         statusAndDur = getReplCoord()->awaitReplication(&txn, time, writeConcern);
@@ -480,11 +480,11 @@ namespace {
                                              BSON("host" << "node4:12345" << "_id" << 3))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = WriteConcernOptions::kNoWaiting;
@@ -555,11 +555,11 @@ namespace {
                                              "multiDCAndRack" << BSON("dc" << 2 << "rack" << 3)))),
                 HostAndPort("node0"));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         // Test invalid write concern
         WriteConcernOptions invalidWriteConcern;
@@ -643,7 +643,7 @@ namespace {
             _result(ReplicationCoordinator::StatusAndDuration(
                     Status::OK(), ReplicationCoordinator::Milliseconds(0))) {}
 
-        void setOpTime(const OpTime& ot) {
+        void setOpTime(const Timestamp& ot) {
             _optime = ot;
         }
 
@@ -681,7 +681,7 @@ namespace {
 
         ReplicationCoordinatorImpl* _replCoord;
         bool _finished;
-        OpTime _optime;
+        Timestamp _optime;
         WriteConcernOptions _writeConcern;
         ReplicationCoordinator::StatusAndDuration _result;
         boost::scoped_ptr<boost::thread> _thread;
@@ -697,13 +697,13 @@ namespace {
                                              BSON("host" << "node3:12345" << "_id" << 2))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         ReplicationAwaiter awaiter(getReplCoord(), &txn);
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = WriteConcernOptions::kNoTimeout;
@@ -748,13 +748,13 @@ namespace {
                                              BSON("host" << "node3:12345" << "_id" << 2))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         ReplicationAwaiter awaiter(getReplCoord(), &txn);
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = 50;
@@ -781,13 +781,13 @@ namespace {
                                              BSON("host" << "node3:12345" << "_id" << 2))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         ReplicationAwaiter awaiter(getReplCoord(), &txn);
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = WriteConcernOptions::kNoTimeout;
@@ -817,13 +817,13 @@ namespace {
                                              BSON("host" << "node3:12345" << "_id" << 2))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         ReplicationAwaiter awaiter(getReplCoord(), &txn);
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = WriteConcernOptions::kNoTimeout;
@@ -893,13 +893,13 @@ namespace {
                                              BSON("_id" << 2 << "host" << "node3"))),
                 HostAndPort("node1"));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
         ReplicationAwaiter awaiter(getReplCoord(), &txn);
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         WriteConcernOptions writeConcern;
         writeConcern.wTimeout = WriteConcernOptions::kNoTimeout;
@@ -947,7 +947,7 @@ namespace {
 
     TEST_F(StepDownTest, StepDownNotPrimary) {
         OperationContextReplMock txn;
-        OpTime optime1(100, 1);
+        Timestamp optime1(100, 1);
         // All nodes are caught up
         getReplCoord()->setMyLastOptime(optime1);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(1, 1, optime1));
@@ -960,7 +960,7 @@ namespace {
 
     TEST_F(StepDownTest, StepDownTimeoutAcquiringGlobalLock) {
         OperationContextReplMock txn;
-        OpTime optime1(100, 1);
+        Timestamp optime1(100, 1);
         // All nodes are caught up
         getReplCoord()->setMyLastOptime(optime1);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(1, 1, optime1));
@@ -978,7 +978,7 @@ namespace {
 
     TEST_F(StepDownTest, StepDownNoWaiting) {
         OperationContextReplMock txn;
-        OpTime optime1(100, 1);
+        Timestamp optime1(100, 1);
         // All nodes are caught up
         getReplCoord()->setMyLastOptime(optime1);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(1, 1, optime1));
@@ -1114,8 +1114,8 @@ namespace {
 
     TEST_F(StepDownTest, StepDownNotCaughtUp) {
         OperationContextReplMock txn;
-        OpTime optime1(100, 1);
-        OpTime optime2(100, 2);
+        Timestamp optime1(100, 1);
+        Timestamp optime2(100, 2);
         // No secondary is caught up
         getReplCoord()->setMyLastOptime(optime2);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(1, 1, optime1));
@@ -1156,8 +1156,8 @@ namespace {
 
     TEST_F(StepDownTest, StepDownCatchUp) {
         OperationContextReplMock txn;
-        OpTime optime1(100, 1);
-        OpTime optime2(100, 2);
+        Timestamp optime1(100, 1);
+        Timestamp optime2(100, 2);
         // No secondary is caught up
         getReplCoord()->setMyLastOptime(optime2);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(1, 1, optime1));
@@ -1204,8 +1204,8 @@ namespace {
 
     TEST_F(StepDownTest, InterruptStepDown) {
         OperationContextNoopWithInterrupt txn;
-        OpTime optime1(100, 1);
-        OpTime optime2(100, 2);
+        Timestamp optime1(100, 1);
+        Timestamp optime2(100, 2);
         // No secondary is caught up
         getReplCoord()->setMyLastOptime(optime2);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(1, 1, optime1));
@@ -1278,9 +1278,9 @@ namespace {
                                              BSON("_id" << 1 << "host" << "test2:1234") <<
                                              BSON("_id" << 2 << "host" << "test3:1234"))),
                 HostAndPort("test1", 1234));
-        OpTime optime1(100, 1);
-        OpTime optime2(100, 2);
-        OpTime optime3(2, 1);
+        Timestamp optime1(100, 1);
+        Timestamp optime2(100, 2);
+        Timestamp optime3(2, 1);
         getReplCoord()->setMyLastOptime(optime1);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(1, 1, optime2));
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(1, 2, optime3));
@@ -1299,12 +1299,12 @@ namespace {
             long long memberId = entry["memberId"].Number();
             memberIds.insert(memberId);
             if (memberId == 0) {
-                ASSERT_EQUALS(optime1, entry["optime"]._opTime());
+                ASSERT_EQUALS(optime1, entry["optime"].timestamp());
             } else if (memberId == 1) {
-                ASSERT_EQUALS(optime2, entry["optime"]._opTime());
+                ASSERT_EQUALS(optime2, entry["optime"].timestamp());
             } else {
                 ASSERT_EQUALS(2, memberId);
-                ASSERT_EQUALS(optime3, entry["optime"]._opTime());
+                ASSERT_EQUALS(optime3, entry["optime"].timestamp());
             }
         }
         ASSERT_EQUALS(3U, memberIds.size()); // Make sure we saw all 3 nodes
@@ -1321,7 +1321,7 @@ namespace {
                 HostAndPort("test2", 1234));
         OperationContextNoop txn;
         getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY);
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
 
         // Can't unset maintenance mode if it was never set to begin with.
         Status status = getReplCoord()->setMaintenanceMode(false);
@@ -1404,8 +1404,8 @@ namespace {
                 HostAndPort("node1", 12345));
         OperationContextNoop txn;
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         getReplCoord()->setMyLastOptime(time2);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(2, 1, time1));
@@ -1434,8 +1434,8 @@ namespace {
         OperationContextNoop txn;
 
         OID client = OID::gen();
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
 
         getExternalState()->setClientHostAndPort(clientHost);
         HandshakeArgs handshake;
@@ -1579,12 +1579,12 @@ namespace {
                                              BSON("host" << "node3:12345" << "_id" << 2))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 0));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 0));
         simulateSuccessfulElection();
 
-        OpTime time1(100, 1);
-        OpTime time2(100, 2);
-        OpTime staleTime(10, 0);
+        Timestamp time1(100, 1);
+        Timestamp time2(100, 2);
+        Timestamp staleTime(10, 0);
         getReplCoord()->setMyLastOptime(time1);
 
         WriteConcernOptions writeConcern;
@@ -1678,10 +1678,10 @@ namespace {
                                              BSON("host" << "node3:12345" << "_id" << 2))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 2));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 2));
         simulateSuccessfulElection();
 
-        OpTime time(100, 2);
+        Timestamp time(100, 2);
 
         // 3 nodes waiting for time
         WriteConcernOptions writeConcern;
@@ -1748,10 +1748,10 @@ namespace {
                                              BSON("host" << "node3:12345" << "_id" << 2))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 2));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 2));
         simulateSuccessfulElection();
 
-        OpTime time(100, 2);
+        Timestamp time(100, 2);
 
         // 3 nodes waiting for time
         WriteConcernOptions writeConcern;
@@ -1805,10 +1805,10 @@ namespace {
                                              BSON("host" << "node5:12345" << "_id" << 4))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        getReplCoord()->setMyLastOptime(OpTime(100, 1));
+        getReplCoord()->setMyLastOptime(Timestamp(100, 1));
         simulateSuccessfulElection();
 
-        OpTime time(100, 2);
+        Timestamp time(100, 2);
 
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(2, 1, time));
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(2, 2, time));
@@ -1878,7 +1878,7 @@ namespace {
                                                   "arbiterOnly" << true))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        OpTime time(100, 0);
+        Timestamp time(100, 0);
         getReplCoord()->setMyLastOptime(time);
         simulateSuccessfulElection();
 
@@ -1919,8 +1919,8 @@ namespace {
                                                   "arbiterOnly" << true))),
                 HostAndPort("node1", 12345));
         ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
-        OpTime zero(0, 0);
-        OpTime time(100, 0);
+        Timestamp zero(0, 0);
+        Timestamp time(100, 0);
         getReplCoord()->setMyLastOptime(time);
         simulateSuccessfulElection();
 
@@ -1935,7 +1935,7 @@ namespace {
 
 
         // Set a new, later OpTime.
-        OpTime newTime = OpTime(100, 1);
+        Timestamp newTime = Timestamp(100, 1);
         getReplCoord()->setMyLastOptime(newTime);
         ASSERT_OK(getReplCoord()->setLastOptime_forTest(2, 3, newTime));
         ASSERT_EQUALS(time, getReplCoord()->getLastCommittedOpTime());
diff --git a/src/mongo/db/repl/replication_coordinator_mock.cpp b/src/mongo/db/repl/replication_coordinator_mock.cpp
index e0efd70392e..99bda38afc0 100644
--- a/src/mongo/db/repl/replication_coordinator_mock.cpp
+++ b/src/mongo/db/repl/replication_coordinator_mock.cpp
@@ -81,7 +81,7 @@ namespace repl {
 
     ReplicationCoordinator::StatusAndDuration ReplicationCoordinatorMock::awaitReplication(
             const OperationContext* txn,
-            const OpTime& ts,
+            const Timestamp& ts,
             const WriteConcernOptions& writeConcern) {
         // TODO
         return StatusAndDuration(Status::OK(), Milliseconds(0));
@@ -123,7 +123,7 @@ namespace repl {
         return false;
     }
 
-    Status ReplicationCoordinatorMock::setLastOptimeForSlave(const OID& rid, const OpTime& ts) {
+    Status ReplicationCoordinatorMock::setLastOptimeForSlave(const OID& rid, const Timestamp& ts) {
         return Status::OK();
     }
     
@@ -131,13 +131,13 @@ namespace repl {
         // TODO
     }
 
-    void ReplicationCoordinatorMock::setMyLastOptime(const OpTime& ts) {}
+    void ReplicationCoordinatorMock::setMyLastOptime(const Timestamp& ts) {}
 
     void ReplicationCoordinatorMock::resetMyLastOptime() {}
 
-    OpTime ReplicationCoordinatorMock::getMyLastOptime() const {
+    Timestamp ReplicationCoordinatorMock::getMyLastOptime() const {
         // TODO
-        return OpTime();
+        return Timestamp();
     }
 
 
@@ -256,7 +256,7 @@ namespace repl {
         return true;
     }
 
-    std::vector<HostAndPort> ReplicationCoordinatorMock::getHostsWrittenTo(const OpTime& op) {
+    std::vector<HostAndPort> ReplicationCoordinatorMock::getHostsWrittenTo(const Timestamp& op) {
         return std::vector<HostAndPort>();
     }
 
@@ -295,8 +295,8 @@ namespace repl {
         invariant(false);
     }
 
-    OpTime ReplicationCoordinatorMock::getLastCommittedOpTime() const {
-        return OpTime();
+    Timestamp ReplicationCoordinatorMock::getLastCommittedOpTime() const {
+        return Timestamp();
     }
 
 } // namespace repl
diff --git a/src/mongo/db/repl/replication_coordinator_mock.h b/src/mongo/db/repl/replication_coordinator_mock.h
index d0a40f1414c..2ec2b344c34 100644
--- a/src/mongo/db/repl/replication_coordinator_mock.h
+++ b/src/mongo/db/repl/replication_coordinator_mock.h
@@ -66,7 +66,7 @@ namespace repl {
 
         virtual ReplicationCoordinator::StatusAndDuration awaitReplication(
                 const OperationContext* txn,
-                const OpTime& ts,
+                const Timestamp& ts,
                 const WriteConcernOptions& writeConcern);
 
         virtual ReplicationCoordinator::StatusAndDuration awaitReplicationOfLastOpForClient(
@@ -91,15 +91,15 @@ namespace repl {
 
         virtual bool shouldIgnoreUniqueIndex(const IndexDescriptor* idx);
 
-        virtual Status setLastOptimeForSlave(const OID& rid, const OpTime& ts);
+        virtual Status setLastOptimeForSlave(const OID& rid, const Timestamp& ts);
 
-        virtual void setMyLastOptime(const OpTime& ts);
+        virtual void setMyLastOptime(const Timestamp& ts);
 
         virtual void resetMyLastOptime();
 
         virtual void setMyHeartbeatMessage(const std::string& msg);
 
-        virtual OpTime getMyLastOptime() const;
+        virtual Timestamp getMyLastOptime() const;
 
         virtual OID getElectionId();
 
@@ -164,7 +164,7 @@ namespace repl {
 
         virtual bool buildsIndexes();
 
-        virtual std::vector<HostAndPort> getHostsWrittenTo(const OpTime& op);
+        virtual std::vector<HostAndPort> getHostsWrittenTo(const Timestamp& op);
 
         virtual std::vector<HostAndPort> getOtherNodesInReplSet() const;
 
@@ -180,7 +180,7 @@ namespace repl {
 
         virtual bool shouldChangeSyncSource(const HostAndPort& currentSource);
 
-        virtual OpTime getLastCommittedOpTime() const;
+        virtual Timestamp getLastCommittedOpTime() const;
     private:
 
         const ReplSettings _settings;
diff --git a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
index 2479c5d4724..808bffe819c 100644
--- a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
+++ b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
@@ -191,7 +191,7 @@ namespace {
                 net->scheduleResponse(noi, net->now(), makeResponseStatus(
                                               BSON("ok" << 1 <<
                                                    "fresher" << false <<
-                                                   "opTime" << Date_t(OpTime(0, 0).asDate()) <<
+                                                   "opTime" << Date_t(Timestamp(0, 0).asULL()) <<
                                                    "veto" << false)));
             }
             else if (request.cmdObj.firstElement().fieldNameStringData() == "replSetElect") {
diff --git a/src/mongo/db/repl/replication_info.cpp b/src/mongo/db/repl/replication_info.cpp
index 8d064089244..dfba98f56aa 100644
--- a/src/mongo/db/repl/replication_info.cpp
+++ b/src/mongo/db/repl/replication_info.cpp
@@ -186,7 +186,7 @@ namespace repl {
             uassert(17347,
                     "Problem reading earliest entry from oplog",
                     Helpers::getSingleton(txn, oplogNS.c_str(), o));
-            result.append("earliestOptime", o["ts"]._opTime());
+            result.append("earliestOptime", o["ts"].timestamp());
             return result.obj();
         }
     } oplogInfoServerStatus;
diff --git a/src/mongo/db/repl/replset_commands.cpp b/src/mongo/db/repl/replset_commands.cpp
index a86ee0e1379..8f090862013 100644
--- a/src/mongo/db/repl/replset_commands.cpp
+++ b/src/mongo/db/repl/replset_commands.cpp
@@ -729,7 +729,7 @@ namespace {
                     "numeric type, but found " << typeName(cfgverElement.type()),
                     cfgverElement.isNumber());
             parsedArgs.cfgver = cfgverElement.safeNumberLong();
-            parsedArgs.opTime = OpTime(cmdObj["opTime"].Date());
+            parsedArgs.opTime = Timestamp(cmdObj["opTime"].Date());
 
             status = getGlobalReplicationCoordinator()->processReplSetFresh(parsedArgs, &result);
             return appendCommandStatus(result, status);
diff --git a/src/mongo/db/repl/rs_initialsync.cpp b/src/mongo/db/repl/rs_initialsync.cpp
index 6fdf3e72190..1380ae190c9 100644
--- a/src/mongo/db/repl/rs_initialsync.cpp
+++ b/src/mongo/db/repl/rs_initialsync.cpp
@@ -32,7 +32,7 @@
 
 #include "mongo/db/repl/rs_initialsync.h"
 
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/bson/util/bson_extract.h"
 #include "mongo/db/auth/authorization_manager.h"
 #include "mongo/db/auth/authorization_manager_global.h"
@@ -207,7 +207,7 @@ namespace {
     bool _initialSyncApplyOplog( OperationContext* ctx,
                                  repl::SyncTail& syncer,
                                  OplogReader* r) {
-        const OpTime startOpTime = getGlobalReplicationCoordinator()->getMyLastOptime();
+        const Timestamp startOpTime = getGlobalReplicationCoordinator()->getMyLastOptime();
         BSONObj lastOp;
         try {
             // It may have been a long time since we last used this connection to
@@ -234,7 +234,7 @@ namespace {
             return false;
         }
 
-        OpTime stopOpTime = lastOp["ts"]._opTime();
+        Timestamp stopOpTime = lastOp["ts"].timestamp();
 
         // If we already have what we need then return.
         if (stopOpTime == startOpTime)
@@ -333,7 +333,7 @@ namespace {
         truncateAndResetOplog(&txn, replCoord, bgsync);
 
         OplogReader r;
-        OpTime now(Milliseconds(curTimeMillis64()).total_seconds(), 0);
+        Timestamp now(Milliseconds(curTimeMillis64()).total_seconds(), 0);
 
         while (r.getHost().empty()) {
             // We must prime the sync source selector so that it considers all candidates regardless
@@ -391,7 +391,7 @@ namespace {
         std::deque<BSONObj> ops;
         ops.push_back(lastOp);
 
-        OpTime lastOptime = writeOpsToOplog(&txn, ops);
+        Timestamp lastOptime = writeOpsToOplog(&txn, ops);
         ReplClientInfo::forClient(txn.getClient()).setLastOp(lastOptime);
         replCoord->setMyLastOptime(lastOptime);
         setNewOptime(lastOptime);
@@ -443,7 +443,7 @@ namespace {
         {
             ScopedTransaction scopedXact(&txn, MODE_IX);
             AutoGetDb autodb(&txn, "local", MODE_X);
-            OpTime lastOpTimeWritten(getGlobalReplicationCoordinator()->getMyLastOptime());
+            Timestamp lastOpTimeWritten(getGlobalReplicationCoordinator()->getMyLastOptime());
             log() << "set minValid=" << lastOpTimeWritten;
 
             // Initial sync is now complete.  Flag this by setting minValid to the last thing
diff --git a/src/mongo/db/repl/rs_rollback.cpp b/src/mongo/db/repl/rs_rollback.cpp
index 22870e6de7e..0d1f4f79929 100644
--- a/src/mongo/db/repl/rs_rollback.cpp
+++ b/src/mongo/db/repl/rs_rollback.cpp
@@ -146,7 +146,7 @@ namespace {
 
         set<string> collectionsToResync;
 
-        OpTime commonPoint;
+        Timestamp commonPoint;
         RecordId commonPointOurDiskloc;
 
         int rbid; // remote server's current rollback sequence #
@@ -286,9 +286,9 @@ namespace {
         if (oplogCursor.get() == NULL || !oplogCursor->more())
             throw RSFatalException("remote oplog empty or unreadable");
 
-        OpTime ourTime = ourObj["ts"]._opTime();
+        Timestamp ourTime = ourObj["ts"].timestamp();
         BSONObj theirObj = oplogCursor->nextSafe();
-        OpTime theirTime = theirObj["ts"]._opTime();
+        Timestamp theirTime = theirObj["ts"].timestamp();
 
         long long diff = static_cast<long long>(ourTime.getSecs())
                                - static_cast<long long>(theirTime.getSecs());
@@ -328,7 +328,7 @@ namespace {
                     throw RSFatalException("RS100 reached beginning of remote oplog [2]");
                 }
                 theirObj = oplogCursor->nextSafe();
-                theirTime = theirObj["ts"]._opTime();
+                theirTime = theirObj["ts"].timestamp();
 
                 if (PlanExecutor::ADVANCED != exec->getNext(&ourObj, &ourLoc)) {
                     severe() << "rollback error RS101 reached beginning of local oplog";
@@ -337,7 +337,7 @@ namespace {
                     log() << "  ourTime:   " << ourTime.toStringLong();
                     throw RSFatalException("RS101 reached beginning of local oplog [1]");
                 }
-                ourTime = ourObj["ts"]._opTime();
+                ourTime = ourObj["ts"].timestamp();
             }
             else if (theirTime > ourTime) {
                 if (!oplogCursor->more()) {
@@ -349,7 +349,7 @@ namespace {
                     throw RSFatalException("RS100 reached beginning of remote oplog [1]");
                 }
                 theirObj = oplogCursor->nextSafe();
-                theirTime = theirObj["ts"]._opTime();
+                theirTime = theirObj["ts"].timestamp();
             }
             else {
                 // theirTime < ourTime
@@ -361,7 +361,7 @@ namespace {
                     log() << "  ourTime:   " << ourTime.toStringLong();
                     throw RSFatalException("RS101 reached beginning of local oplog [2]");
                 }
-                ourTime = ourObj["ts"]._opTime();
+                ourTime = ourObj["ts"].timestamp();
             }
         }
     }
@@ -449,7 +449,7 @@ namespace {
 
         // we have items we are writing that aren't from a point-in-time.  thus best not to come
         // online until we get to that point in freshness.
-        OpTime minValid = newMinValid["ts"]._opTime();
+        Timestamp minValid = newMinValid["ts"].timestamp();
         log() << "minvalid=" << minValid.toStringLong();
         setMinValid(txn, minValid);
 
@@ -499,7 +499,7 @@ namespace {
                     err = "can't get minvalid from sync source";
                 }
                 else {
-                    OpTime minValid = newMinValid["ts"]._opTime();
+                    Timestamp minValid = newMinValid["ts"].timestamp();
                     log() << "minvalid=" << minValid.toStringLong();
                     setMinValid(txn, minValid);
                 }
@@ -807,13 +807,13 @@ namespace {
 } // namespace
 
     void syncRollback(OperationContext* txn,
-                      OpTime lastOpTimeApplied,
+                      Timestamp lastOpTimeApplied,
                       OplogReader* oplogreader, 
                       ReplicationCoordinator* replCoord) {
         // check that we are at minvalid, otherwise we cannot rollback as we may be in an
         // inconsistent state
         {
-            OpTime minvalid = getMinValid(txn);
+            Timestamp minvalid = getMinValid(txn);
             if( minvalid > lastOpTimeApplied ) {
                 severe() << "need to rollback, but in inconsistent state" << endl;
                 log() << "minvalid: " << minvalid.toString() << " our last optime: "
diff --git a/src/mongo/db/repl/rs_rollback.h b/src/mongo/db/repl/rs_rollback.h
index 8c5644f816a..55f1b887d92 100644
--- a/src/mongo/db/repl/rs_rollback.h
+++ b/src/mongo/db/repl/rs_rollback.h
@@ -30,7 +30,7 @@
 
 namespace mongo {
     class OperationContext;
-    class OpTime;
+    class Timestamp;
 
 namespace repl {
     class OplogReader; 
@@ -59,7 +59,7 @@ namespace repl {
      */
 
     void syncRollback(OperationContext* txn,
-                      OpTime lastOpTimeWritten,
+                      Timestamp lastOpTimeWritten,
                       OplogReader* oplogreader,
                       ReplicationCoordinator* replCoord);
 
diff --git a/src/mongo/db/repl/sync_source_feedback.h b/src/mongo/db/repl/sync_source_feedback.h
index 0e3fccccfac..054f6d6b183 100644
--- a/src/mongo/db/repl/sync_source_feedback.h
+++ b/src/mongo/db/repl/sync_source_feedback.h
@@ -31,7 +31,7 @@
 
 #include <boost/scoped_ptr.hpp>
 #include <boost/thread/mutex.hpp>
-#include <boost/thread/condition_variable.hpp>
+#include <boost/thread/condition.hpp>
 
 #include "mongo/client/constants.h"
 #include "mongo/client/dbclientcursor.h"
diff --git a/src/mongo/db/repl/sync_tail.cpp b/src/mongo/db/repl/sync_tail.cpp
index 7b6349a1738..40f70579704 100644
--- a/src/mongo/db/repl/sync_tail.cpp
+++ b/src/mongo/db/repl/sync_tail.cpp
@@ -266,7 +266,7 @@ namespace repl {
     }
 
     // Doles out all the work to the writer pool threads and waits for them to complete
-    OpTime SyncTail::multiApply(OperationContext* txn, std::deque<BSONObj>& ops) {
+    Timestamp SyncTail::multiApply(OperationContext* txn, std::deque<BSONObj>& ops) {
 
         if (getGlobalServiceContext()->getGlobalStorageEngine()->isMmapV1()) {
             // Use a ThreadPool to prefetch all the operations in a batch.
@@ -297,13 +297,13 @@ namespace repl {
         applyOps(writerVectors);
 
         if (inShutdown()) {
-            return OpTime();
+            return Timestamp();
         }
 
         if (mustAwaitCommit) {
             txn->recoveryUnit()->goingToAwaitCommit();
         }
-        OpTime lastOpTime = writeOpsToOplog(txn, ops);
+        Timestamp lastOpTime = writeOpsToOplog(txn, ops);
         // Wait for journal before setting last op time if any op in batch had j:true
         if (mustAwaitCommit) {
             txn->recoveryUnit()->awaitCommit();
@@ -359,12 +359,12 @@ namespace repl {
             (*writerVectors)[hash % writerVectors->size()].push_back(*it);
         }
     }
-    void SyncTail::oplogApplication(OperationContext* txn, const OpTime& endOpTime) {
+    void SyncTail::oplogApplication(OperationContext* txn, const Timestamp& endOpTime) {
         _applyOplogUntil(txn, endOpTime);
     }
 
     /* applies oplog from "now" until endOpTime using the applier threads for initial sync*/
-    void SyncTail::_applyOplogUntil(OperationContext* txn, const OpTime& endOpTime) {
+    void SyncTail::_applyOplogUntil(OperationContext* txn, const Timestamp& endOpTime) {
         unsigned long long bytesApplied = 0;
         unsigned long long entriesApplied = 0;
         while (true) {
@@ -376,7 +376,7 @@ namespace repl {
 
                 // Check if we reached the end
                 const BSONObj currentOp = ops.back();
-                const OpTime currentOpTime = currentOp["ts"]._opTime();
+                const Timestamp currentOpTime = currentOp["ts"].timestamp();
 
                 // When we reach the end return this batch
                 if (currentOpTime == endOpTime) {
@@ -406,7 +406,7 @@ namespace repl {
             bytesApplied += ops.getSize();
             entriesApplied += ops.getDeque().size();
 
-            const OpTime lastOpTime = multiApply(txn, ops.getDeque());
+            const Timestamp lastOpTime = multiApply(txn, ops.getDeque());
 
             if (inShutdown()) {
                 return;
@@ -442,7 +442,7 @@ namespace {
             return;
         }
 
-        OpTime minvalid = getMinValid(txn);
+        Timestamp minvalid = getMinValid(txn);
         if (minvalid > replCoord->getMyLastOptime()) {
             return;
         }
@@ -495,7 +495,7 @@ namespace {
                 const int slaveDelaySecs = replCoord->getSlaveDelaySecs().total_seconds();
                 if (!ops.empty() && slaveDelaySecs > 0) {
                     const BSONObj& lastOp = ops.getDeque().back();
-                    const unsigned int opTimestampSecs = lastOp["ts"]._opTime().getSecs();
+                    const unsigned int opTimestampSecs = lastOp["ts"].timestamp().getSecs();
 
                     // Stop the batch as the lastOp is too new to be applied. If we continue
                     // on, we can get ops that are way ahead of the delay and this will
@@ -527,7 +527,7 @@ namespace {
             // Set minValid to the last op to be applied in this next batch.
             // This will cause this node to go into RECOVERING state
             // if we should crash and restart before updating the oplog
-            OpTime minValid = lastOp["ts"]._opTime();
+            Timestamp minValid = lastOp["ts"].timestamp();
             setMinValid(&txn, minValid);
             multiApply(&txn, ops.getDeque());
         }
@@ -617,7 +617,7 @@ namespace {
         // ignore slaveDelay if the box is still initializing. once
         // it becomes secondary we can worry about it.
         if( slaveDelaySecs > 0 && replCoord->getMemberState().secondary() ) {
-            const OpTime ts = lastOp["ts"]._opTime();
+            const Timestamp ts = lastOp["ts"].timestamp();
             long long a = ts.getSecs();
             long long b = time(0);
             long long lag = b - a;
diff --git a/src/mongo/db/repl/sync_tail.h b/src/mongo/db/repl/sync_tail.h
index 5932634362e..68e5f546845 100644
--- a/src/mongo/db/repl/sync_tail.h
+++ b/src/mongo/db/repl/sync_tail.h
@@ -57,7 +57,7 @@ namespace repl {
         /**
          * Runs _applyOplogUntil(stopOpTime)
          */
-        virtual void oplogApplication(OperationContext* txn, const OpTime& stopOpTime);
+        virtual void oplogApplication(OperationContext* txn, const Timestamp& stopOpTime);
 
         void oplogApplication();
         bool peek(BSONObj* obj);
@@ -101,14 +101,14 @@ namespace repl {
         // Prefetch and write a deque of operations, using the supplied function.
         // Initial Sync and Sync Tail each use a different function.
         // Returns the last OpTime applied.
-        OpTime multiApply(OperationContext* txn, std::deque<BSONObj>& ops);
+        Timestamp multiApply(OperationContext* txn, std::deque<BSONObj>& ops);
 
         /**
          * Applies oplog entries until reaching "endOpTime".
          *
          * NOTE:Will not transition or check states
          */
-        void _applyOplogUntil(OperationContext* txn, const OpTime& endOpTime);
+        void _applyOplogUntil(OperationContext* txn, const Timestamp& endOpTime);
 
     private:
         BackgroundSyncInterface* _networkQueue;
diff --git a/src/mongo/db/repl/topology_coordinator.h b/src/mongo/db/repl/topology_coordinator.h
index 1da4aa09642..fe8edd37333 100644
--- a/src/mongo/db/repl/topology_coordinator.h
+++ b/src/mongo/db/repl/topology_coordinator.h
@@ -41,7 +41,7 @@
 namespace mongo {
 
     class OperationContext;
-    class OpTime;
+    class Timestamp;
 
 namespace repl {
 
@@ -117,7 +117,7 @@ namespace repl {
         /**
          * Chooses and sets a new sync source, based on our current knowledge of the world.
          */
-        virtual HostAndPort chooseNewSyncSource(Date_t now, const OpTime& lastOpApplied) = 0;
+        virtual HostAndPort chooseNewSyncSource(Date_t now, const Timestamp& lastOpApplied) = 0;
 
         /**
          * Suppresses selecting "host" as sync source until "until".
@@ -185,21 +185,21 @@ namespace repl {
         // produces a reply to a replSetSyncFrom command
         virtual void prepareSyncFromResponse(const ReplicationExecutor::CallbackData& data,
                                              const HostAndPort& target,
-                                             const OpTime& lastOpApplied,
+                                             const Timestamp& lastOpApplied,
                                              BSONObjBuilder* response,
                                              Status* result) = 0;
 
         // produce a reply to a replSetFresh command
         virtual void prepareFreshResponse(const ReplicationCoordinator::ReplSetFreshArgs& args,
                                           Date_t now,
-                                          OpTime lastOpApplied,
+                                          Timestamp lastOpApplied,
                                           BSONObjBuilder* response,
                                           Status* result) = 0;
 
         // produce a reply to a received electCmd
         virtual void prepareElectResponse(const ReplicationCoordinator::ReplSetElectArgs& args,
                                           Date_t now,
-                                          OpTime lastOpApplied,
+                                          Timestamp lastOpApplied,
                                           BSONObjBuilder* response,
                                           Status* result) = 0;
 
@@ -207,14 +207,14 @@ namespace repl {
         virtual Status prepareHeartbeatResponse(Date_t now,
                                                 const ReplSetHeartbeatArgs& args,
                                                 const std::string& ourSetName,
-                                                const OpTime& lastOpApplied,
+                                                const Timestamp& lastOpApplied,
                                                 ReplSetHeartbeatResponse* response) = 0;
 
         // produce a reply to a status request
         virtual void prepareStatusResponse(const ReplicationExecutor::CallbackData& data,
                                            Date_t now,
                                            unsigned uptime,
-                                           const OpTime& lastOpApplied,
+                                           const Timestamp& lastOpApplied,
                                            BSONObjBuilder* response,
                                            Status* result) = 0;
 
@@ -246,7 +246,7 @@ namespace repl {
         virtual void updateConfig(const ReplicaSetConfig& newConfig,
                                   int selfIndex,
                                   Date_t now,
-                                  OpTime lastOpApplied) = 0;
+                                  Timestamp lastOpApplied) = 0;
 
         /**
          * Prepares a heartbeat request appropriate for sending to "target", assuming the
@@ -296,7 +296,7 @@ namespace repl {
                 Milliseconds networkRoundTripTime,
                 const HostAndPort& target,
                 const StatusWith<ReplSetHeartbeatResponse>& hbResponse,
-                OpTime myLastOpApplied) = 0;
+                Timestamp myLastOpApplied) = 0;
 
         /**
          * If getRole() == Role::candidate and this node has not voted too recently, updates the
@@ -312,7 +312,7 @@ namespace repl {
          * Exactly one of either processWinElection or processLoseElection must be called if
          * processHeartbeatResponse returns StartElection, to exit candidate mode.
          */
-        virtual void processWinElection(OID electionId, OpTime electionOpTime) = 0;
+        virtual void processWinElection(OID electionId, Timestamp electionOpTime) = 0;
 
         /**
          * Performs state updates associated with losing an election.
@@ -332,7 +332,7 @@ namespace repl {
          *
          * Returns whether or not the step down succeeded.
          */
-        virtual bool stepDown(Date_t until, bool force, OpTime lastOpApplied) = 0;
+        virtual bool stepDown(Date_t until, bool force, Timestamp lastOpApplied) = 0;
 
         /**
          * Sometimes a request to step down comes in (like via a heartbeat), but we don't have the
@@ -348,7 +348,7 @@ namespace repl {
          * Considers whether or not this node should stand for election, and returns true
          * if the node has transitioned to candidate role as a result of the call.
          */
-        virtual bool checkShouldStandForElection(Date_t now, const OpTime& lastOpApplied) = 0;
+        virtual bool checkShouldStandForElection(Date_t now, const Timestamp& lastOpApplied) = 0;
 
         /**
          * Set the outgoing heartbeat message from self
diff --git a/src/mongo/db/repl/topology_coordinator_impl.cpp b/src/mongo/db/repl/topology_coordinator_impl.cpp
index 7e964ef0d8b..1d019eec216 100644
--- a/src/mongo/db/repl/topology_coordinator_impl.cpp
+++ b/src/mongo/db/repl/topology_coordinator_impl.cpp
@@ -149,7 +149,7 @@ namespace {
     }
 
     HostAndPort TopologyCoordinatorImpl::chooseNewSyncSource(Date_t now, 
-                                                             const OpTime& lastOpApplied) {
+                                                             const Timestamp& lastOpApplied) {
         // If we are primary, then we aren't syncing from anyone (else).
         if (_iAmPrimary()) {
             return HostAndPort();
@@ -211,23 +211,23 @@ namespace {
 
         // Find primary's oplog time. Reject sync candidates that are more than
         // maxSyncSourceLagSecs seconds behind.
-        OpTime primaryOpTime;
+        Timestamp primaryOpTime;
         if (_currentPrimaryIndex != -1) {
             primaryOpTime = _hbdata[_currentPrimaryIndex].getOpTime();
         }
         else {
             // choose a time that will exclude no candidates, since we don't see a primary
-            primaryOpTime = OpTime(_maxSyncSourceLagSecs.total_seconds(), 0);
+            primaryOpTime = Timestamp(_maxSyncSourceLagSecs.total_seconds(), 0);
         }
 
         if (primaryOpTime.getSecs() < 
             static_cast<unsigned int>(_maxSyncSourceLagSecs.total_seconds())) {
             // erh - I think this means there was just a new election
             // and we don't yet know the new primary's optime
-            primaryOpTime = OpTime(_maxSyncSourceLagSecs.total_seconds(), 0);
+            primaryOpTime = Timestamp(_maxSyncSourceLagSecs.total_seconds(), 0);
         }
 
-        OpTime oldestSyncOpTime(primaryOpTime.getSecs() - _maxSyncSourceLagSecs.total_seconds(), 0);
+        Timestamp oldestSyncOpTime(primaryOpTime.getSecs() - _maxSyncSourceLagSecs.total_seconds(), 0);
 
         int closestIndex = -1;
 
@@ -348,7 +348,7 @@ namespace {
     void TopologyCoordinatorImpl::prepareSyncFromResponse(
             const ReplicationExecutor::CallbackData& data,
             const HostAndPort& target,
-            const OpTime& lastOpApplied,
+            const Timestamp& lastOpApplied,
             BSONObjBuilder* response,
             Status* result) {
         if (data.status == ErrorCodes::CallbackCanceled) {
@@ -442,7 +442,7 @@ namespace {
     void TopologyCoordinatorImpl::prepareFreshResponse(
             const ReplicationCoordinator::ReplSetFreshArgs& args,
             const Date_t now,
-            const OpTime lastOpApplied,
+            const Timestamp lastOpApplied,
             BSONObjBuilder* response,
             Status* result) {
 
@@ -478,7 +478,7 @@ namespace {
         else if (args.opTime < _latestKnownOpTime(lastOpApplied)) {
             weAreFresher = true;
         }
-        response->appendDate("opTime", lastOpApplied.asDate());
+        response->appendDate("opTime", lastOpApplied.asULL());
         response->append("fresher", weAreFresher);
 
         std::string errmsg;
@@ -493,7 +493,7 @@ namespace {
     bool TopologyCoordinatorImpl::_shouldVetoMember(
             const ReplicationCoordinator::ReplSetFreshArgs& args,
             const Date_t& now,
-            const OpTime& lastOpApplied,
+            const Timestamp& lastOpApplied,
             std::string* errmsg) const {
 
         if (_rsConfig.getConfigVersion() < args.cfgver) {
@@ -564,7 +564,7 @@ namespace {
     void TopologyCoordinatorImpl::prepareElectResponse(
             const ReplicationCoordinator::ReplSetElectArgs& args,
             const Date_t now,
-            const OpTime lastOpApplied,
+            const Timestamp lastOpApplied,
             BSONObjBuilder* response,
             Status* result) {
 
@@ -648,7 +648,7 @@ namespace {
             Date_t now,
             const ReplSetHeartbeatArgs& args,
             const std::string& ourSetName,
-            const OpTime& lastOpApplied,
+            const Timestamp& lastOpApplied,
             ReplSetHeartbeatResponse* response) {
 
         if (args.getProtocolVersion() != 1) {
@@ -802,7 +802,7 @@ namespace {
             Milliseconds networkRoundTripTime,
             const HostAndPort& target,
             const StatusWith<ReplSetHeartbeatResponse>& hbResponse,
-            OpTime myLastOpApplied) {
+            Timestamp myLastOpApplied) {
 
         const MemberState originalState = getMemberState();
         PingStats& hbStats = _pings[target];
@@ -928,7 +928,7 @@ namespace {
             int updatedConfigIndex,
             const MemberState& originalState,
             Date_t now,
-            const OpTime& lastOpApplied) {
+            const Timestamp& lastOpApplied) {
 
         // This method has two interrelated responsibilities, performed in two phases.
         //
@@ -970,13 +970,13 @@ namespace {
                     _rsConfig.getMemberAt(_currentPrimaryIndex);
                 const MemberConfig& highestPriorityMember =
                     _rsConfig.getMemberAt(highestPriorityIndex);
-                const OpTime highestPriorityMemberOptime = highestPriorityIndex == _selfIndex ?
+                const Timestamp highestPriorityMemberOptime = highestPriorityIndex == _selfIndex ?
                         lastOpApplied : _hbdata[highestPriorityIndex].getOpTime();
 
                 if ((highestPriorityMember.getPriority() > currentPrimaryMember.getPriority()) &&
                         _isOpTimeCloseEnoughToLatestToElect(highestPriorityMemberOptime,
                                                             lastOpApplied)) {
-                    const OpTime latestOpTime = _latestKnownOpTime(lastOpApplied);
+                    const Timestamp latestOpTime = _latestKnownOpTime(lastOpApplied);
 
                     if (_iAmPrimary()) {
                         if (_stepDownPending) {
@@ -1050,7 +1050,7 @@ namespace {
 
                 // If we are also primary, this is a problem.  Determine who should step down.
                 if (_iAmPrimary()) {
-                    OpTime remoteElectionTime = _hbdata[remotePrimaryIndex].getElectionTime();
+                    Timestamp remoteElectionTime = _hbdata[remotePrimaryIndex].getElectionTime();
                     log() << "another primary seen with election time "
                           << remoteElectionTime << " my election time is " << _electionTime;
 
@@ -1122,7 +1122,7 @@ namespace {
     }
 
     bool TopologyCoordinatorImpl::checkShouldStandForElection(
-            Date_t now, const OpTime& lastOpApplied) {
+            Date_t now, const Timestamp& lastOpApplied) {
         if (_currentPrimaryIndex != -1) {
             return false;
         }
@@ -1170,8 +1170,8 @@ namespace {
     }
 
     bool TopologyCoordinatorImpl::_isOpTimeCloseEnoughToLatestToElect(
-            const OpTime& otherOpTime, const OpTime& ourLastOpApplied) const {
-        const OpTime latestKnownOpTime = _latestKnownOpTime(ourLastOpApplied);
+            const Timestamp& otherOpTime, const Timestamp& ourLastOpApplied) const {
+        const Timestamp latestKnownOpTime = _latestKnownOpTime(ourLastOpApplied);
         // Use addition instead of subtraction to avoid overflow.
         return otherOpTime.getSecs() + 10 >= (latestKnownOpTime.getSecs());
     }
@@ -1184,8 +1184,8 @@ namespace {
         return false;
     }
 
-    OpTime TopologyCoordinatorImpl::_latestKnownOpTime(OpTime ourLastOpApplied) const {
-        OpTime latest = ourLastOpApplied;
+    Timestamp TopologyCoordinatorImpl::_latestKnownOpTime(Timestamp ourLastOpApplied) const {
+        Timestamp latest = ourLastOpApplied;
 
         for (std::vector<MemberHeartbeatData>::const_iterator it = _hbdata.begin();
              it != _hbdata.end(); 
@@ -1198,7 +1198,7 @@ namespace {
                 continue;
             }
 
-            OpTime optime = it->getOpTime();
+            Timestamp optime = it->getOpTime();
 
             if (optime > latest) {
                 latest = optime;
@@ -1221,7 +1221,7 @@ namespace {
     }
 
     int TopologyCoordinatorImpl::_getHighestPriorityElectableIndex(
-            Date_t now, OpTime lastOpApplied) const {
+            Date_t now, Timestamp lastOpApplied) const {
         int maxIndex = -1;
         for (int currentIndex = 0; currentIndex < _rsConfig.getNumMembers(); currentIndex++) {
             UnelectableReasonMask reason = currentIndex == _selfIndex ?
@@ -1236,7 +1236,7 @@ namespace {
     }
 
     void TopologyCoordinatorImpl::changeMemberState_forTest(const MemberState& newMemberState,
-                                                            OpTime electionTime) {
+                                                            Timestamp electionTime) {
         invariant(_selfIndex != -1);
         if (newMemberState == getMemberState())
             return;
@@ -1262,7 +1262,7 @@ namespace {
                     ReplicaSetConfig(),
                     -1,
                     Date_t(),
-                    OpTime());
+                    Timestamp());
             break;
         default:
             severe() << "Cannot switch to state " << newMemberState;
@@ -1287,7 +1287,7 @@ namespace {
             if (primaryIndex != -1) {
                 ReplSetHeartbeatResponse hbResponse;
                 hbResponse.setState(MemberState::RS_PRIMARY);
-                hbResponse.setElectionTime(OpTime());
+                hbResponse.setElectionTime(Timestamp());
                 hbResponse.setOpTime(_hbdata[primaryIndex].getOpTime());
                 hbResponse.setSyncingTo("");
                 hbResponse.setHbMsg("");
@@ -1311,7 +1311,7 @@ namespace {
             const ReplicationExecutor::CallbackData& data,
             Date_t now,
             unsigned selfUptime,
-            const OpTime& lastOpApplied,
+            const Timestamp& lastOpApplied,
             BSONObjBuilder* response,
             Status* result) {
         if (data.status == ErrorCodes::CallbackCanceled) {
@@ -1577,7 +1577,7 @@ namespace {
         }
     }
 
-    OpTime TopologyCoordinatorImpl::getElectionTime() const {
+    Timestamp TopologyCoordinatorImpl::getElectionTime() const {
         return _electionTime;
     }
 
@@ -1631,7 +1631,7 @@ namespace {
     void TopologyCoordinatorImpl::updateConfig(const ReplicaSetConfig& newConfig,
                                                int selfIndex,
                                                Date_t now,
-                                               OpTime lastOpApplied) {
+                                               Timestamp lastOpApplied) {
         invariant(_role != Role::candidate);
         invariant(selfIndex < newConfig.getNumMembers());
 
@@ -1689,7 +1689,7 @@ namespace {
 
     TopologyCoordinatorImpl::UnelectableReasonMask TopologyCoordinatorImpl::_getUnelectableReason(
             int index,
-            const OpTime& lastOpApplied) const {
+            const Timestamp& lastOpApplied) const {
         invariant(index != _selfIndex);
         const MemberConfig& memberConfig = _rsConfig.getMemberAt(index);
         const MemberHeartbeatData& hbData = _hbdata[index];
@@ -1715,7 +1715,7 @@ namespace {
 
     TopologyCoordinatorImpl::UnelectableReasonMask TopologyCoordinatorImpl::_getMyUnelectableReason(
             const Date_t now,
-            const OpTime lastApplied) const {
+            const Timestamp lastApplied) const {
 
         UnelectableReasonMask result = None;
         if (lastApplied.isNull()) {
@@ -1838,7 +1838,7 @@ namespace {
         return _pings[host].getMillis();
     }
 
-    void TopologyCoordinatorImpl::_setElectionTime(const OpTime& newElectionTime) {
+    void TopologyCoordinatorImpl::_setElectionTime(const Timestamp& newElectionTime) {
         _electionTime = newElectionTime;
     }
 
@@ -1913,7 +1913,7 @@ namespace {
 
     void TopologyCoordinatorImpl::processWinElection(
             OID electionId,
-            OpTime electionOpTime) {
+            Timestamp electionOpTime) {
         invariant(_role == Role::candidate);
         _electionTime = electionOpTime;
         _electionId = electionId;
@@ -1926,7 +1926,7 @@ namespace {
     void TopologyCoordinatorImpl::processLoseElection() {
         invariant(_role == Role::candidate);
         const HostAndPort syncSourceAddress = getSyncSourceAddress();
-        _electionTime = OpTime(0, 0);
+        _electionTime = Timestamp(0, 0);
         _electionId = OID();
         _role = Role::follower;
 
@@ -1937,7 +1937,7 @@ namespace {
         }
     }
 
-    bool TopologyCoordinatorImpl::stepDown(Date_t until, bool force, OpTime lastOpApplied) {
+    bool TopologyCoordinatorImpl::stepDown(Date_t until, bool force, Timestamp lastOpApplied) {
         bool canStepDown = force;
         for (int i = 0; !canStepDown && i < _rsConfig.getNumMembers(); ++i) {
             if (i == _selfIndex) {
@@ -2051,7 +2051,7 @@ namespace {
         }
         invariant(currentMemberIndex != _selfIndex);
 
-        OpTime currentOpTime = _hbdata[currentMemberIndex].getOpTime();
+        Timestamp currentOpTime = _hbdata[currentMemberIndex].getOpTime();
         if (currentOpTime.isNull()) {
             // Haven't received a heartbeat from the sync source yet, so can't tell if we should
             // change.
diff --git a/src/mongo/db/repl/topology_coordinator_impl.h b/src/mongo/db/repl/topology_coordinator_impl.h
index 3e9c9a48c18..e8d0d42a46a 100644
--- a/src/mongo/db/repl/topology_coordinator_impl.h
+++ b/src/mongo/db/repl/topology_coordinator_impl.h
@@ -31,7 +31,7 @@
 #include <string>
 #include <vector>
 
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/repl/member_heartbeat_data.h"
 #include "mongo/db/repl/member_state.h"
 #include "mongo/db/repl/replica_set_config.h"
@@ -127,7 +127,7 @@ namespace repl {
         virtual int getMaintenanceCount() const;
         virtual void setForceSyncSourceIndex(int index);
         virtual HostAndPort chooseNewSyncSource(Date_t now, 
-                                                const OpTime& lastOpApplied);
+                                                const Timestamp& lastOpApplied);
         virtual void blacklistSyncSource(const HostAndPort& host, Date_t until);
         virtual void unblacklistSyncSource(const HostAndPort& host, Date_t now);
         virtual void clearSyncSourceBlacklist();
@@ -138,28 +138,28 @@ namespace repl {
         virtual void adjustMaintenanceCountBy(int inc);
         virtual void prepareSyncFromResponse(const ReplicationExecutor::CallbackData& data,
                                              const HostAndPort& target,
-                                             const OpTime& lastOpApplied,
+                                             const Timestamp& lastOpApplied,
                                              BSONObjBuilder* response,
                                              Status* result);
         virtual void prepareFreshResponse(const ReplicationCoordinator::ReplSetFreshArgs& args,
                                           Date_t now,
-                                          OpTime lastOpApplied,
+                                          Timestamp lastOpApplied,
                                           BSONObjBuilder* response,
                                           Status* result);
         virtual void prepareElectResponse(const ReplicationCoordinator::ReplSetElectArgs& args,
                                           Date_t now,
-                                          OpTime lastOpApplied,
+                                          Timestamp lastOpApplied,
                                           BSONObjBuilder* response,
                                           Status* result);
         virtual Status prepareHeartbeatResponse(Date_t now,
                                                 const ReplSetHeartbeatArgs& args,
                                                 const std::string& ourSetName,
-                                                const OpTime& lastOpApplied,
+                                                const Timestamp& lastOpApplied,
                                                 ReplSetHeartbeatResponse* response);
         virtual void prepareStatusResponse(const ReplicationExecutor::CallbackData& data,
                                            Date_t now,
                                            unsigned uptime,
-                                           const OpTime& lastOpApplied,
+                                           const Timestamp& lastOpApplied,
                                            BSONObjBuilder* response,
                                            Status* result);
         virtual void fillIsMasterForReplSet(IsMasterResponse* response);
@@ -167,7 +167,7 @@ namespace repl {
         virtual void updateConfig(const ReplicaSetConfig& newConfig,
                                   int selfIndex,
                                   Date_t now,
-                                  OpTime lastOpApplied);
+                                  Timestamp lastOpApplied);
         virtual std::pair<ReplSetHeartbeatArgs, Milliseconds> prepareHeartbeatRequest(
                 Date_t now,
                 const std::string& ourSetName,
@@ -177,13 +177,13 @@ namespace repl {
                 Milliseconds networkRoundTripTime,
                 const HostAndPort& target,
                 const StatusWith<ReplSetHeartbeatResponse>& hbResponse,
-                OpTime myLastOpApplied);
+                Timestamp myLastOpApplied);
         virtual bool voteForMyself(Date_t now);
-        virtual void processWinElection(OID electionId, OpTime electionOpTime);
+        virtual void processWinElection(OID electionId, Timestamp electionOpTime);
         virtual void processLoseElection();
-        virtual bool checkShouldStandForElection(Date_t now, const OpTime& lastOpApplied);
+        virtual bool checkShouldStandForElection(Date_t now, const Timestamp& lastOpApplied);
         virtual void setMyHeartbeatMessage(const Date_t now, const std::string& message);
-        virtual bool stepDown(Date_t until, bool force, OpTime lastOpApplied);
+        virtual bool stepDown(Date_t until, bool force, Timestamp lastOpApplied);
         virtual bool stepDownIfPending();
         virtual Date_t getStepDownTime() const;
 
@@ -195,10 +195,10 @@ namespace repl {
 
         // Changes _memberState to newMemberState.  Only for testing.
         void changeMemberState_forTest(const MemberState& newMemberState,
-                                       OpTime electionTime = OpTime(0,0));
+                                       Timestamp electionTime = Timestamp(0,0));
 
         // Sets "_electionTime" to "newElectionTime".  Only for testing.
-        void _setElectionTime(const OpTime& newElectionTime);
+        void _setElectionTime(const Timestamp& newElectionTime);
 
         // Sets _currentPrimaryIndex to the given index.  Should only be used in unit tests!
         // TODO(spencer): Remove this once we can easily call for an election in unit tests to
@@ -206,7 +206,7 @@ namespace repl {
         void _setCurrentPrimaryForTest(int primaryIndex);
 
         // Returns _electionTime.  Only used in unittests.
-        OpTime getElectionTime() const;
+        Timestamp getElectionTime() const;
 
         // Returns _electionId.  Only used in unittests.
         OID getElectionId() const;
@@ -242,7 +242,7 @@ namespace repl {
         // If we veto, the errmsg will be filled in with a reason
         bool _shouldVetoMember(const ReplicationCoordinator::ReplSetFreshArgs& args,
                                const Date_t& now,
-                               const OpTime& lastOpApplied,
+                               const Timestamp& lastOpApplied,
                                std::string* errmsg) const;
 
         // Returns the index of the member with the matching id, or -1 if none match.
@@ -253,18 +253,18 @@ namespace repl {
 
         // Is otherOpTime close enough (within 10 seconds) to the latest known optime to qualify
         // for an election
-        bool _isOpTimeCloseEnoughToLatestToElect(const OpTime& otherOpTime,
-                                                 const OpTime& ourLastOpApplied) const;
+        bool _isOpTimeCloseEnoughToLatestToElect(const Timestamp& otherOpTime,
+                                                 const Timestamp& ourLastOpApplied) const;
 
         // Returns reason why "self" member is unelectable
         UnelectableReasonMask _getMyUnelectableReason(
                 const Date_t now,
-                const OpTime lastOpApplied) const;
+                const Timestamp lastOpApplied) const;
 
         // Returns reason why memberIndex is unelectable
         UnelectableReasonMask _getUnelectableReason(
                 int memberIndex,
-                const OpTime& lastOpApplied) const;
+                const Timestamp& lastOpApplied) const;
 
         // Returns the nice text of why the node is unelectable
         std::string _getUnelectableReasonString(UnelectableReasonMask ur) const;
@@ -273,10 +273,10 @@ namespace repl {
         bool _iAmPrimary() const;
 
         // Scans through all members that are 'up' and return the latest known optime.
-        OpTime _latestKnownOpTime(OpTime ourLastOpApplied) const;
+        Timestamp _latestKnownOpTime(Timestamp ourLastOpApplied) const;
 
         // Scans the electable set and returns the highest priority member index
-        int _getHighestPriorityElectableIndex(Date_t now, OpTime lastOpApplied) const;
+        int _getHighestPriorityElectableIndex(Date_t now, Timestamp lastOpApplied) const;
 
         // Returns true if "one" member is higher priority than "two" member
         bool _isMemberHigherPriority(int memberOneIndex, int memberTwoIndex) const;
@@ -294,7 +294,7 @@ namespace repl {
                 int updatedConfigIndex,
                 const MemberState& originalState,
                 Date_t now,
-                const OpTime& lastOpApplied);
+                const Timestamp& lastOpApplied);
 
         /**
          * Updates _hbdata based on the newConfig, ensuring that every member in the newConfig
@@ -325,7 +325,7 @@ namespace repl {
         // result of an election.
         OID _electionId;
         // The time at which the current PRIMARY was elected.
-        OpTime _electionTime;
+        Timestamp _electionTime;
 
         // the index of the member we currently believe is primary, if one exists, otherwise -1
         int _currentPrimaryIndex;
diff --git a/src/mongo/db/repl/topology_coordinator_impl_test.cpp b/src/mongo/db/repl/topology_coordinator_impl_test.cpp
index 2ec2cd2b89c..ce99ca62ee9 100644
--- a/src/mongo/db/repl/topology_coordinator_impl_test.cpp
+++ b/src/mongo/db/repl/topology_coordinator_impl_test.cpp
@@ -83,7 +83,7 @@ namespace {
                                             needle));
         }
 
-        void makeSelfPrimary(const OpTime& electionOpTime = OpTime(0,0)) {
+        void makeSelfPrimary(const Timestamp& electionOpTime = Timestamp(0,0)) {
             getTopoCoord().changeMemberState_forTest(MemberState::RS_PRIMARY, electionOpTime);
             getTopoCoord()._setCurrentPrimaryForTest(_selfIndex);
         }
@@ -100,7 +100,7 @@ namespace {
         void updateConfig(BSONObj cfg,
                           int selfIndex,
                           Date_t now = Date_t(-1),
-                          OpTime lastOp = OpTime()) {
+                          Timestamp lastOp = Timestamp()) {
             ReplicaSetConfig config;
             ASSERT_OK(config.initialize(cfg));
             ASSERT_OK(config.validate());
@@ -121,9 +121,9 @@ namespace {
                 const HostAndPort& member,
                 const std::string& setName,
                 MemberState memberState,
-                OpTime electionTime,
-                OpTime lastOpTimeSender,
-                OpTime lastOpTimeReceiver) {
+                Timestamp electionTime,
+                Timestamp lastOpTimeSender,
+                Timestamp lastOpTimeReceiver) {
             return _receiveHeartbeatHelper(Status::OK(),
                                            member,
                                            setName,
@@ -137,14 +137,14 @@ namespace {
         HeartbeatResponseAction receiveDownHeartbeat(
                 const HostAndPort& member,
                 const std::string& setName,
-                OpTime lastOpTimeReceiver,
+                Timestamp lastOpTimeReceiver,
                 ErrorCodes::Error errcode = ErrorCodes::HostUnreachable) {
             return _receiveHeartbeatHelper(Status(errcode, ""),
                                            member,
                                            setName,
                                            MemberState::RS_UNKNOWN,
-                                           OpTime(),
-                                           OpTime(),
+                                           Timestamp(),
+                                           Timestamp(),
                                            lastOpTimeReceiver,
                                            Milliseconds(0));
         }
@@ -152,15 +152,15 @@ namespace {
         HeartbeatResponseAction heartbeatFromMember(const HostAndPort& member,
                                                     const std::string& setName,
                                                     MemberState memberState,
-                                                    OpTime lastOpTimeSender,
+                                                    Timestamp lastOpTimeSender,
                                                     Milliseconds roundTripTime = Milliseconds(0)) {
             return _receiveHeartbeatHelper(Status::OK(),
                                            member,
                                            setName,
                                            memberState,
-                                           OpTime(),
+                                           Timestamp(),
                                            lastOpTimeSender,
-                                           OpTime(),
+                                           Timestamp(),
                                            roundTripTime);
         }
 
@@ -170,9 +170,9 @@ namespace {
                                                         const HostAndPort& member,
                                                         const std::string& setName,
                                                         MemberState memberState,
-                                                        OpTime electionTime,
-                                                        OpTime lastOpTimeSender,
-                                                        OpTime lastOpTimeReceiver,
+                                                        Timestamp electionTime,
+                                                        Timestamp lastOpTimeSender,
+                                                        Timestamp lastOpTimeReceiver,
                                                         Milliseconds roundTripTime) {
             StatusWith<ReplSetHeartbeatResponse> hbResponse =
                     StatusWith<ReplSetHeartbeatResponse>(responseStatus);
@@ -204,7 +204,7 @@ namespace {
 
     TEST_F(TopoCoordTest, ChooseSyncSourceBasic) {
         // if we do not have an index in the config, we should get an empty syncsource
-        HostAndPort newSyncSource = getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        HostAndPort newSyncSource = getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_TRUE(newSyncSource.empty());
 
         updateConfig(BSON("_id" << "rs0" <<
@@ -217,49 +217,49 @@ namespace {
         setSelfMemberState(MemberState::RS_SECONDARY);
 
         // member h2 is the furthest ahead
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, OpTime(1,0));
-        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, Timestamp(1,0));
+        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, Timestamp(0,0));
 
         // We start with no sync source
         ASSERT(getTopoCoord().getSyncSourceAddress().empty());
 
         // Fail due to insufficient number of pings
-        newSyncSource = getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        newSyncSource = getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(getTopoCoord().getSyncSourceAddress(), newSyncSource);
         ASSERT(getTopoCoord().getSyncSourceAddress().empty());
 
         // Record 2nd round of pings to allow choosing a new sync source; all members equidistant
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, OpTime(1,0));
-        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, Timestamp(1,0));
+        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, Timestamp(0,0));
 
         // Should choose h2, since it is furthest ahead
-        newSyncSource = getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        newSyncSource = getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(getTopoCoord().getSyncSourceAddress(), newSyncSource);
         ASSERT_EQUALS(HostAndPort("h2"), getTopoCoord().getSyncSourceAddress());
         
         // h3 becomes further ahead, so it should be chosen
-        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, OpTime(2,0));
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, Timestamp(2,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
 
         // h3 becomes an invalid candidate for sync source; should choose h2 again
-        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_RECOVERING, OpTime(2,0));
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_RECOVERING, Timestamp(2,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h2"), getTopoCoord().getSyncSourceAddress());
 
         // h3 back in SECONDARY and ahead
-        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, OpTime(2,0));
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, Timestamp(2,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
 
         // h3 goes down
-        receiveDownHeartbeat(HostAndPort("h3"), "rs0", OpTime());
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        receiveDownHeartbeat(HostAndPort("h3"), "rs0", Timestamp());
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h2"), getTopoCoord().getSyncSourceAddress());
 
         // h3 back up and ahead
-        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, OpTime(2,0));
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, Timestamp(2,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
 
     }
@@ -282,43 +282,43 @@ namespace {
                      0);
 
         setSelfMemberState(MemberState::RS_SECONDARY);
-        OpTime lastOpTimeWeApplied = OpTime(100,0);
+        Timestamp lastOpTimeWeApplied = Timestamp(100,0);
 
         heartbeatFromMember(HostAndPort("h1"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(700));
+                            Timestamp(501, 0), Milliseconds(700));
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(600));
+                            Timestamp(501, 0), Milliseconds(600));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(500));
+                            Timestamp(501, 0), Milliseconds(500));
         heartbeatFromMember(HostAndPort("h4"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(400));
+                            Timestamp(501, 0), Milliseconds(400));
         heartbeatFromMember(HostAndPort("h5"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(300));
+                            Timestamp(501, 0), Milliseconds(300));
 
         // This node is lagged further than maxSyncSourceLagSeconds.
         heartbeatFromMember(HostAndPort("h6"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(499, 0), Milliseconds(200));
+                            Timestamp(499, 0), Milliseconds(200));
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         heartbeatFromMember(HostAndPort("hprimary"), "rs0", MemberState::RS_PRIMARY,
-                            OpTime(600, 0), Milliseconds(100));
+                            Timestamp(600, 0), Milliseconds(100));
         ASSERT_EQUALS(7, getCurrentPrimaryIndex());
 
         // Record 2nd round of pings to allow choosing a new sync source
         heartbeatFromMember(HostAndPort("h1"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(700));
+                            Timestamp(501, 0), Milliseconds(700));
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(600));
+                            Timestamp(501, 0), Milliseconds(600));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(500));
+                            Timestamp(501, 0), Milliseconds(500));
         heartbeatFromMember(HostAndPort("h4"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(400));
+                            Timestamp(501, 0), Milliseconds(400));
         heartbeatFromMember(HostAndPort("h5"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(501, 0), Milliseconds(300));
+                            Timestamp(501, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h6"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(499, 0), Milliseconds(200));
+                            Timestamp(499, 0), Milliseconds(200));
         heartbeatFromMember(HostAndPort("hprimary"), "rs0", MemberState::RS_PRIMARY,
-                            OpTime(600, 0), Milliseconds(100));
+                            Timestamp(600, 0), Milliseconds(100));
 
         // Should choose primary first; it's closest
         getTopoCoord().chooseNewSyncSource(now()++, lastOpTimeWeApplied);
@@ -326,7 +326,7 @@ namespace {
 
         // Primary goes far far away
         heartbeatFromMember(HostAndPort("hprimary"), "rs0", MemberState::RS_PRIMARY,
-                            OpTime(600, 0), Milliseconds(100000000));
+                            Timestamp(600, 0), Milliseconds(100000000));
 
         // Should choose h4.  (if an arbiter has an oplog, it's a valid sync source)
         // h6 is not considered because it is outside the maxSyncLagSeconds window,
@@ -334,29 +334,29 @@ namespace {
         ASSERT_EQUALS(HostAndPort("h4"), getTopoCoord().getSyncSourceAddress());
         
         // h4 goes down; should choose h1
-        receiveDownHeartbeat(HostAndPort("h4"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h4"), "rs0", Timestamp());
         getTopoCoord().chooseNewSyncSource(now()++, lastOpTimeWeApplied);
         ASSERT_EQUALS(HostAndPort("h1"), getTopoCoord().getSyncSourceAddress());
 
         // Primary and h1 go down; should choose h6 
-        receiveDownHeartbeat(HostAndPort("h1"), "rs0", OpTime());
-        receiveDownHeartbeat(HostAndPort("hprimary"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h1"), "rs0", Timestamp());
+        receiveDownHeartbeat(HostAndPort("hprimary"), "rs0", Timestamp());
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         getTopoCoord().chooseNewSyncSource(now()++, lastOpTimeWeApplied);
         ASSERT_EQUALS(HostAndPort("h6"), getTopoCoord().getSyncSourceAddress());
 
         // h6 goes down; should choose h5
-        receiveDownHeartbeat(HostAndPort("h6"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h6"), "rs0", Timestamp());
         getTopoCoord().chooseNewSyncSource(now()++, lastOpTimeWeApplied);
         ASSERT_EQUALS(HostAndPort("h5"), getTopoCoord().getSyncSourceAddress());
 
         // h5 goes down; should choose h3
-        receiveDownHeartbeat(HostAndPort("h5"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h5"), "rs0", Timestamp());
         getTopoCoord().chooseNewSyncSource(now()++, lastOpTimeWeApplied);
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
 
         // h3 goes down; no sync source candidates remain
-        receiveDownHeartbeat(HostAndPort("h3"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h3"), "rs0", Timestamp());
         getTopoCoord().chooseNewSyncSource(now()++, lastOpTimeWeApplied);
         ASSERT(getTopoCoord().getSyncSourceAddress().empty());
     }
@@ -375,27 +375,27 @@ namespace {
         setSelfMemberState(MemberState::RS_SECONDARY);
 
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(100));
+                            Timestamp(1, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(100));
+                            Timestamp(1, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(0, 0), Milliseconds(300));
+                            Timestamp(0, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(0, 0), Milliseconds(300));
+                            Timestamp(0, 0), Milliseconds(300));
 
         // No primary situation: should choose no sync source.
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT(getTopoCoord().getSyncSourceAddress().empty());
         
         // Add primary
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_PRIMARY,
-                            OpTime(0, 0), Milliseconds(300));
+                            Timestamp(0, 0), Milliseconds(300));
         ASSERT_EQUALS(2, getCurrentPrimaryIndex());
 
         // h3 is primary and should be chosen as sync source, despite being further away than h2
         // and the primary (h3) being behind our most recently applied optime
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(10,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(10,0));
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
 
     }
@@ -412,20 +412,20 @@ namespace {
         setSelfMemberState(MemberState::RS_SECONDARY);
 
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(100));
+                            Timestamp(1, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(100));
+                            Timestamp(1, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(0, 0), Milliseconds(300));
+                            Timestamp(0, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(0, 0), Milliseconds(300));
+                            Timestamp(0, 0), Milliseconds(300));
 
         // No primary situation: should choose h2 sync source.
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h2"), getTopoCoord().getSyncSourceAddress());
 
         // Become primary
-        makeSelfPrimary(OpTime(3.0));
+        makeSelfPrimary(Timestamp(3.0));
         ASSERT_EQUALS(0, getCurrentPrimaryIndex());
 
         // Check sync source
@@ -445,27 +445,27 @@ namespace {
 
         // two rounds of heartbeat pings from each member
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(300));
+                            Timestamp(1, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(300));
+                            Timestamp(1, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
 
         // force should overrule other defaults
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
         getTopoCoord().setForceSyncSourceIndex(1);
         // force should cause shouldChangeSyncSource() to return true
         // even if the currentSource is the force target
         ASSERT_TRUE(getTopoCoord().shouldChangeSyncSource(HostAndPort("h2"), now()));
         ASSERT_TRUE(getTopoCoord().shouldChangeSyncSource(HostAndPort("h3"), now()));
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h2"), getTopoCoord().getSyncSourceAddress());
 
         // force should only work for one call to chooseNewSyncSource
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
     }
 
@@ -481,25 +481,25 @@ namespace {
         setSelfMemberState(MemberState::RS_SECONDARY);
 
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(300));
+                            Timestamp(1, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(300));
+                            Timestamp(1, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
 
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
         
         Date_t expireTime = 100;
         getTopoCoord().blacklistSyncSource(HostAndPort("h3"), expireTime);
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         // Should choose second best choice now that h3 is blacklisted.
         ASSERT_EQUALS(HostAndPort("h2"), getTopoCoord().getSyncSourceAddress());
 
         // After time has passed, should go back to original sync source
-        getTopoCoord().chooseNewSyncSource(expireTime, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(expireTime, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h3"), getTopoCoord().getSyncSourceAddress());
     }
 
@@ -516,27 +516,27 @@ namespace {
         setSelfMemberState(MemberState::RS_SECONDARY);
 
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_PRIMARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_PRIMARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
         ASSERT_EQUALS(1, getCurrentPrimaryIndex());
 
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
 
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h2"), getTopoCoord().getSyncSourceAddress());
 
         Date_t expireTime = 100;
         getTopoCoord().blacklistSyncSource(HostAndPort("h2"), expireTime);
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         // Can't choose any sync source now.
         ASSERT(getTopoCoord().getSyncSourceAddress().empty());
 
         // After time has passed, should go back to the primary
-        getTopoCoord().chooseNewSyncSource(expireTime, OpTime(0,0));
+        getTopoCoord().chooseNewSyncSource(expireTime, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h2"), getTopoCoord().getSyncSourceAddress());
     }
 
@@ -553,38 +553,38 @@ namespace {
 
         // Generate enough heartbeats to select a sync source below
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(300));
+                            Timestamp(1, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(1, 0), Milliseconds(300));
+                            Timestamp(1, 0), Milliseconds(300));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY,
-                            OpTime(2, 0), Milliseconds(100));
+                            Timestamp(2, 0), Milliseconds(100));
 
         ASSERT_EQUALS(HostAndPort("h3"),
-                      getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0)));
+                      getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0)));
         ASSERT_EQUALS(MemberState::RS_SECONDARY, getTopoCoord().getMemberState().s);
         // Good state setup done
 
         // Mark nodes down, ensure that we have no source and are secondary
-        receiveDownHeartbeat(HostAndPort("h2"), "rs0", OpTime(), ErrorCodes::NetworkTimeout);
-        receiveDownHeartbeat(HostAndPort("h3"), "rs0", OpTime(), ErrorCodes::NetworkTimeout);
-        ASSERT_TRUE(getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0)).empty());
+        receiveDownHeartbeat(HostAndPort("h2"), "rs0", Timestamp(), ErrorCodes::NetworkTimeout);
+        receiveDownHeartbeat(HostAndPort("h3"), "rs0", Timestamp(), ErrorCodes::NetworkTimeout);
+        ASSERT_TRUE(getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0)).empty());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, getTopoCoord().getMemberState().s);
 
         // Mark nodes down + unauth, ensure that we have no source and are secondary
-        receiveDownHeartbeat(HostAndPort("h2"), "rs0", OpTime(), ErrorCodes::NetworkTimeout);
-        receiveDownHeartbeat(HostAndPort("h3"), "rs0", OpTime(), ErrorCodes::Unauthorized);
-        ASSERT_TRUE(getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0)).empty());
+        receiveDownHeartbeat(HostAndPort("h2"), "rs0", Timestamp(), ErrorCodes::NetworkTimeout);
+        receiveDownHeartbeat(HostAndPort("h3"), "rs0", Timestamp(), ErrorCodes::Unauthorized);
+        ASSERT_TRUE(getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0)).empty());
         ASSERT_EQUALS(MemberState::RS_RECOVERING, getTopoCoord().getMemberState().s);
 
         // Having an auth error but with another node up should bring us out of RECOVERING
         HeartbeatResponseAction action = receiveUpHeartbeat(HostAndPort("h2"),
                                                             "rs0",
                                                             MemberState::RS_SECONDARY,
-                                                            OpTime(0, 0),
-                                                            OpTime(2, 0),
-                                                            OpTime(2, 0));
+                                                            Timestamp(0, 0),
+                                                            Timestamp(2, 0),
+                                                            Timestamp(2, 0));
         ASSERT_EQUALS(MemberState::RS_SECONDARY, getTopoCoord().getMemberState().s);
         // Test that the heartbeat that brings us from RECOVERING to SECONDARY doesn't initiate
         // an election (SERVER-17164)
@@ -600,12 +600,12 @@ namespace {
                               BSON("_id" << 30 << "host" << "h3"))),
                      -1);
         ASSERT_NO_ACTION(heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY,
-                                      OpTime(1, 0), Milliseconds(300)).getAction());
+                                      Timestamp(1, 0), Milliseconds(300)).getAction());
     }
 
     TEST_F(TopoCoordTest, PrepareSyncFromResponse) {
-        OpTime staleOpTime(1, 1);
-        OpTime ourOpTime(staleOpTime.getSecs() + 11, 1);
+        Timestamp staleOpTime(1, 1);
+        Timestamp ourOpTime(staleOpTime.getSecs() + 11, 1);
          
         Status result = Status::OK();
         BSONObjBuilder response;
@@ -689,7 +689,7 @@ namespace {
                       result.reason());
 
         // Try to sync from a member that is down
-        receiveDownHeartbeat(HostAndPort("h4"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h4"), "rs0", Timestamp());
 
         BSONObjBuilder response7;
         getTopoCoord().prepareSyncFromResponse(
@@ -731,12 +731,12 @@ namespace {
         BSONObj response10Obj = response10.obj();
         ASSERT_FALSE(response10Obj.hasField("warning"));
         ASSERT_EQUALS(HostAndPort("h6").toString(), response10Obj["prevSyncTarget"].String());
-        receiveDownHeartbeat(HostAndPort("h6"), "rs0", OpTime());
-        HostAndPort syncSource = getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        receiveDownHeartbeat(HostAndPort("h6"), "rs0", Timestamp());
+        HostAndPort syncSource = getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h6"), syncSource);
 
         // Try to sync from a member that is unauth'd
-        receiveDownHeartbeat(HostAndPort("h5"), "rs0", OpTime(), ErrorCodes::Unauthorized);
+        receiveDownHeartbeat(HostAndPort("h5"), "rs0", Timestamp(), ErrorCodes::Unauthorized);
 
         BSONObjBuilder response11;
         getTopoCoord().prepareSyncFromResponse(
@@ -753,7 +753,7 @@ namespace {
         getTopoCoord().prepareSyncFromResponse(
                 cbData(), HostAndPort("h6"), ourOpTime, &response12, &result);
         ASSERT_OK(result);
-        syncSource = getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        syncSource = getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
         ASSERT_EQUALS(HostAndPort("h6"), syncSource);
     }
 
@@ -771,8 +771,8 @@ namespace {
         Date_t heartbeatTime = 5000;
         Seconds uptimeSecs(10);
         Date_t curTime = heartbeatTime + uptimeSecs.total_milliseconds();
-        OpTime electionTime(1, 2);
-        OpTime oplogProgress(3, 4);
+        Timestamp electionTime(1, 2);
+        Timestamp oplogProgress(3, 4);
         std::string setName = "mySet";
 
         updateConfig(BSON("_id" << setName <<
@@ -793,7 +793,7 @@ namespace {
                                                 Milliseconds(0),
                                                 member,
                                                 hbResponse,
-                                                OpTime(0,0));
+                                                Timestamp(0,0));
 
         member = HostAndPort("test1:1234");
         ReplSetHeartbeatResponse hb;
@@ -810,7 +810,7 @@ namespace {
                                                 Milliseconds(4000),
                                                 member,
                                                 hbResponse,
-                                                OpTime(0,0));
+                                                Timestamp(0,0));
         makeSelfPrimary();
 
         // Now node 0 is down, node 1 is up, and for node 2 we have no heartbeat data yet.
@@ -841,9 +841,9 @@ namespace {
         ASSERT_EQUALS(MemberState::RS_DOWN, member0Status["state"].numberInt());
         ASSERT_EQUALS("(not reachable/healthy)", member0Status["stateStr"].str());
         ASSERT_EQUALS(0, member0Status["uptime"].numberInt());
-        ASSERT_EQUALS(OpTime(), OpTime(member0Status["optime"].timestampValue()));
+        ASSERT_EQUALS(Timestamp(), Timestamp(member0Status["optime"].timestampValue()));
         ASSERT_TRUE(member0Status.hasField("optimeDate"));
-        ASSERT_EQUALS(Date_t(OpTime().getSecs() * 1000ULL),
+        ASSERT_EQUALS(Date_t(Timestamp().getSecs() * 1000ULL),
                       member0Status["optimeDate"].Date().millis);
         ASSERT_EQUALS(heartbeatTime, member0Status["lastHeartbeat"].date());
         ASSERT_EQUALS(Date_t(), member0Status["lastHeartbeatRecv"].date());
@@ -856,7 +856,7 @@ namespace {
         ASSERT_EQUALS(MemberState(MemberState::RS_SECONDARY).toString(),
                       member1Status["stateStr"].String());
         ASSERT_EQUALS(uptimeSecs.total_seconds(), member1Status["uptime"].numberInt());
-        ASSERT_EQUALS(oplogProgress, OpTime(member1Status["optime"].timestampValue()));
+        ASSERT_EQUALS(oplogProgress, Timestamp(member1Status["optime"].timestampValue()));
         ASSERT_TRUE(member1Status.hasField("optimeDate"));
         ASSERT_EQUALS(Date_t(oplogProgress.getSecs() * 1000ULL),
                       member1Status["optimeDate"].Date().millis);
@@ -888,7 +888,7 @@ namespace {
         ASSERT_EQUALS(MemberState(MemberState::RS_PRIMARY).toString(),
                       selfStatus["stateStr"].str());
         ASSERT_EQUALS(uptimeSecs.total_seconds(), selfStatus["uptime"].numberInt());
-        ASSERT_EQUALS(oplogProgress, OpTime(selfStatus["optime"].timestampValue()));
+        ASSERT_EQUALS(oplogProgress, Timestamp(selfStatus["optime"].timestampValue()));
         ASSERT_TRUE(selfStatus.hasField("optimeDate"));
         ASSERT_EQUALS(Date_t(oplogProgress.getSecs() * 1000ULL),
                       selfStatus["optimeDate"].Date().millis);
@@ -903,7 +903,7 @@ namespace {
         Date_t heartbeatTime = 5000;
         Seconds uptimeSecs(10);
         Date_t curTime = heartbeatTime + uptimeSecs.total_milliseconds();
-        OpTime oplogProgress(3, 4);
+        Timestamp oplogProgress(3, 4);
         std::string setName = "mySet";
 
         updateConfig(BSON("_id" << setName <<
@@ -928,9 +928,9 @@ namespace {
 
     TEST_F(TopoCoordTest, PrepareFreshResponse) {
         ReplicationCoordinator::ReplSetFreshArgs args;
-        OpTime freshestOpTime(15, 10);
-        OpTime ourOpTime(10, 10);
-        OpTime staleOpTime(1, 1);
+        Timestamp freshestOpTime(15, 10);
+        Timestamp ourOpTime(10, 10);
+        Timestamp staleOpTime(1, 1);
         Status internalErrorStatus(ErrorCodes::InternalError, "didn't set status");
 
         // if we do not have an index in the config, we should get ErrorCodes::ReplicaSetNotFound
@@ -978,7 +978,7 @@ namespace {
         ASSERT_OK(status1);
         BSONObj response1 = responseBuilder1.obj();
         ASSERT_EQUALS("config version stale", response1["info"].String());
-        ASSERT_EQUALS(ourOpTime, OpTime(response1["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response1["opTime"].timestampValue()));
         ASSERT_TRUE(response1["fresher"].Bool());
         ASSERT_FALSE(response1["veto"].Bool());
         ASSERT_FALSE(response1.hasField("errmsg"));
@@ -993,7 +993,7 @@ namespace {
         getTopoCoord().prepareFreshResponse(args, Date_t(), ourOpTime, &responseBuilder2, &status2);
         ASSERT_OK(status2);
         BSONObj response2 = responseBuilder2.obj();
-        ASSERT_EQUALS(ourOpTime, OpTime(response2["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response2["opTime"].timestampValue()));
         ASSERT_FALSE(response2["fresher"].Bool());
         ASSERT_TRUE(response2["veto"].Bool());
         ASSERT_EQUALS("replSet couldn't find member with id 0", response2["errmsg"].String());
@@ -1011,7 +1011,7 @@ namespace {
         ASSERT_OK(status3);
         BSONObj response3 = responseBuilder3.obj();
         ASSERT_FALSE(response3.hasField("info"));
-        ASSERT_EQUALS(ourOpTime, OpTime(response3["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response3["opTime"].timestampValue()));
         ASSERT_FALSE(response3["fresher"].Bool());
         ASSERT_TRUE(response3["veto"].Bool());
         ASSERT_EQUALS("I am already primary, h1:27017 can try again once I've stepped down",
@@ -1029,7 +1029,7 @@ namespace {
         ASSERT_OK(status4);
         BSONObj response4 = responseBuilder4.obj();
         ASSERT_FALSE(response4.hasField("info"));
-        ASSERT_EQUALS(ourOpTime, OpTime(response4["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response4["opTime"].timestampValue()));
         ASSERT_FALSE(response4["fresher"].Bool());
         ASSERT_TRUE(response4["veto"].Bool());
         ASSERT_EQUALS(
@@ -1049,7 +1049,7 @@ namespace {
         ASSERT_OK(status5);
         BSONObj response5 = responseBuilder5.obj();
         ASSERT_FALSE(response5.hasField("info"));
-        ASSERT_EQUALS(ourOpTime, OpTime(response5["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response5["opTime"].timestampValue()));
         ASSERT_FALSE(response5["fresher"].Bool());
         ASSERT_TRUE(response5["veto"].Bool());
         ASSERT(response5["errmsg"].String().find("h1:27017 has lower priority of 1 than") !=
@@ -1059,7 +1059,7 @@ namespace {
         args.id = 40;
         args.who = HostAndPort("h3");
 
-        receiveDownHeartbeat(HostAndPort("h3"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h3"), "rs0", Timestamp());
 
         BSONObjBuilder responseBuilder6;
         Status status6 = internalErrorStatus;
@@ -1067,7 +1067,7 @@ namespace {
         ASSERT_OK(status6);
         BSONObj response6 = responseBuilder6.obj();
         ASSERT_FALSE(response6.hasField("info"));
-        ASSERT_EQUALS(ourOpTime, OpTime(response6["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response6["opTime"].timestampValue()));
         ASSERT_FALSE(response6["fresher"].Bool());
         ASSERT_TRUE(response6["veto"].Bool());
         ASSERT_NE(std::string::npos, response6["errmsg"].String().find(
@@ -1085,7 +1085,7 @@ namespace {
         ASSERT_OK(status7);
         BSONObj response7 = responseBuilder7.obj();
         ASSERT_FALSE(response7.hasField("info"));
-        ASSERT_EQUALS(ourOpTime, OpTime(response7["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response7["opTime"].timestampValue()));
         ASSERT_FALSE(response7["fresher"].Bool());
         ASSERT_TRUE(response7["veto"].Bool());
         ASSERT_NE(std::string::npos, response7["errmsg"].String().find(
@@ -1101,7 +1101,7 @@ namespace {
         ASSERT_OK(status8);
         BSONObj response8 = responseBuilder8.obj();
         ASSERT_FALSE(response8.hasField("info"));
-        ASSERT_EQUALS(ourOpTime, OpTime(response8["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response8["opTime"].timestampValue()));
         ASSERT_FALSE(response8["fresher"].Bool());
         ASSERT_TRUE(response8["veto"].Bool());
         ASSERT_NE(std::string::npos, response8["errmsg"].String().find(
@@ -1117,7 +1117,7 @@ namespace {
         ASSERT_OK(status9);
         BSONObj response9 = responseBuilder9.obj();
         ASSERT_FALSE(response9.hasField("info"));
-        ASSERT_EQUALS(ourOpTime, OpTime(response9["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response9["opTime"].timestampValue()));
         ASSERT_FALSE(response9["fresher"].Bool());
         ASSERT_TRUE(response9["veto"].Bool());
         ASSERT_NE(std::string::npos, response9["errmsg"].String().find(
@@ -1139,7 +1139,7 @@ namespace {
         ASSERT_OK(status10);
         BSONObj response10 = responseBuilder10.obj();
         ASSERT_FALSE(response10.hasField("info"));
-        ASSERT_EQUALS(ourOpTime, OpTime(response10["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response10["opTime"].timestampValue()));
         ASSERT_TRUE(response10["fresher"].Bool());
         ASSERT_TRUE(response10["veto"].Bool());
         ASSERT_TRUE(response10.hasField("errmsg"));
@@ -1149,7 +1149,7 @@ namespace {
         args.id = 40;
         args.who = HostAndPort("h3");
 
-        receiveDownHeartbeat(HostAndPort("h2"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h2"), "rs0", Timestamp());
         heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, ourOpTime);
 
         BSONObjBuilder responseBuilder11;
@@ -1159,7 +1159,7 @@ namespace {
         ASSERT_OK(status11);
         BSONObj response11 = responseBuilder11.obj();
         ASSERT_FALSE(response11.hasField("info")) << response11.toString();
-        ASSERT_EQUALS(ourOpTime, OpTime(response11["opTime"].timestampValue()));
+        ASSERT_EQUALS(ourOpTime, Timestamp(response11["opTime"].timestampValue()));
         ASSERT_FALSE(response11["fresher"].Bool()) << response11.toString();
         ASSERT_FALSE(response11["veto"].Bool()) << response11.toString();
         ASSERT_FALSE(response11.hasField("errmsg")) << response11.toString();
@@ -1219,7 +1219,7 @@ namespace {
                         _target,
                         StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::ExceededTimeLimit,
                                                              "Took too long"),
-                        OpTime(0, 0));  // We've never applied anything.
+                        Timestamp(0, 0));  // We've never applied anything.
 
             ASSERT_EQUALS(HeartbeatResponseAction::NoAction, action.getAction());
             ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
@@ -1261,7 +1261,7 @@ namespace {
                         Milliseconds(400), // Spent 0.4 of the 0.5 seconds in the network.
                         target(),
                         StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::NodeNotFound, "Bad DNS?"),
-                        OpTime(0, 0));  // We've never applied anything.
+                        Timestamp(0, 0));  // We've never applied anything.
             ASSERT_EQUALS(HeartbeatResponseAction::NoAction, action.getAction());
             ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
             // Because the first retry failed without timing out, we expect to retry immediately.
@@ -1295,7 +1295,7 @@ namespace {
     };
 
     TEST_F(HeartbeatResponseHighVerbosityTest, UpdateHeartbeatDataNodeBelivesWeAreDown) {
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         // request heartbeat
         std::pair<ReplSetHeartbeatArgs, Milliseconds> request =
@@ -1321,7 +1321,7 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseHighVerbosityTest, UpdateHeartbeatDataMemberNotInConfig) {
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         // request heartbeat
         std::pair<ReplSetHeartbeatArgs, Milliseconds> request =
@@ -1346,7 +1346,7 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseHighVerbosityTest, UpdateHeartbeatDataSameConfig) {
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         // request heartbeat
         std::pair<ReplSetHeartbeatArgs, Milliseconds> request =
@@ -1385,7 +1385,7 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseHighVerbosityTest, UpdateHeartbeatDataOldConfig) {
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         // request heartbeat
         std::pair<ReplSetHeartbeatArgs, Milliseconds> request =
@@ -1438,7 +1438,7 @@ namespace {
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(reconfigResponse),
-                    OpTime(0, 0));  // We've never applied anything.
+                    Timestamp(0, 0));  // We've never applied anything.
         ASSERT_EQUALS(HeartbeatResponseAction::Reconfig, action.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
         ASSERT_EQUALS(Date_t(firstRequestDate() + 6500), action.getNextHeartbeatStartDate());
@@ -1450,7 +1450,7 @@ namespace {
 
         // make self primary
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
-        makeSelfPrimary(OpTime(5,0));
+        makeSelfPrimary(Timestamp(5,0));
         ASSERT_EQUALS(0, getCurrentPrimaryIndex());
 
         ReplSetHeartbeatResponse electedMoreRecentlyResponse;
@@ -1458,7 +1458,7 @@ namespace {
         electedMoreRecentlyResponse.setSetName("rs0");
         electedMoreRecentlyResponse.setState(MemberState::RS_PRIMARY);
         electedMoreRecentlyResponse.setElectable(true);
-        electedMoreRecentlyResponse.setElectionTime(OpTime(3,0));
+        electedMoreRecentlyResponse.setElectionTime(Timestamp(3,0));
         electedMoreRecentlyResponse.setVersion(5);
         HeartbeatResponseAction action =
             getTopoCoord().processHeartbeatResponse(
@@ -1466,7 +1466,7 @@ namespace {
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(electedMoreRecentlyResponse),
-                    OpTime(0,0));  // We've never applied anything.
+                    Timestamp(0,0));  // We've never applied anything.
         ASSERT_EQUALS(HeartbeatResponseAction::StepDownRemotePrimary, action.getAction());
         ASSERT_EQUALS(1, action.getPrimaryConfigIndex());
         ASSERT_EQUALS(Date_t(firstRequestDate() + 6500), action.getNextHeartbeatStartDate());
@@ -1479,7 +1479,7 @@ namespace {
         // acknowledge the other member so that we see a majority
         HeartbeatResponseAction action = receiveDownHeartbeat(HostAndPort("host3"),
                                                               "rs0",
-                                                              OpTime(100, 0));
+                                                              Timestamp(100, 0));
         ASSERT_NO_ACTION(action.getAction());
 
         // make us PRIMARY
@@ -1490,7 +1490,7 @@ namespace {
         electedMoreRecentlyResponse.setSetName("rs0");
         electedMoreRecentlyResponse.setState(MemberState::RS_PRIMARY);
         electedMoreRecentlyResponse.setElectable(false);
-        electedMoreRecentlyResponse.setElectionTime(OpTime(10,0));
+        electedMoreRecentlyResponse.setElectionTime(Timestamp(10,0));
         electedMoreRecentlyResponse.setVersion(5);
         action =
             getTopoCoord().processHeartbeatResponse(
@@ -1498,7 +1498,7 @@ namespace {
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(electedMoreRecentlyResponse),
-                    OpTime(0, 0));  // We've never applied anything.
+                    Timestamp(0, 0));  // We've never applied anything.
         ASSERT_EQUALS(HeartbeatResponseAction::StepDownSelf, action.getAction());
         ASSERT_EQUALS(0, action.getPrimaryConfigIndex());
         ASSERT_EQUALS(Date_t(firstRequestDate() + 6500), action.getNextHeartbeatStartDate());
@@ -1516,8 +1516,8 @@ namespace {
         // action.
         
         // acknowledge the other member so that we see a majority
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
         HeartbeatResponseAction action = receiveUpHeartbeat(HostAndPort("host3"),
                                                             "rs0",
                                                             MemberState::RS_SECONDARY,
@@ -1564,7 +1564,7 @@ namespace {
                     Milliseconds(100), // Spent 0.1 of the 0.3 seconds in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::NodeNotFound, "Bad DNS?"),
-                    OpTime(0, 0));  // We've never applied anything.
+                    Timestamp(0, 0));  // We've never applied anything.
         ASSERT_EQUALS(HeartbeatResponseAction::NoAction, action.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
         // Because this is the second retry, rather than retry again, we expect to wait for the
@@ -1578,7 +1578,7 @@ namespace {
 
         // make self primary
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
-        makeSelfPrimary(OpTime(5,0));
+        makeSelfPrimary(Timestamp(5,0));
         ASSERT_EQUALS(0, getCurrentPrimaryIndex());
 
         ReplSetHeartbeatResponse electedMoreRecentlyResponse;
@@ -1586,7 +1586,7 @@ namespace {
         electedMoreRecentlyResponse.setSetName("rs0");
         electedMoreRecentlyResponse.setState(MemberState::RS_PRIMARY);
         electedMoreRecentlyResponse.setElectable(true);
-        electedMoreRecentlyResponse.setElectionTime(OpTime(3,0));
+        electedMoreRecentlyResponse.setElectionTime(Timestamp(3,0));
         electedMoreRecentlyResponse.setVersion(5);
         HeartbeatResponseAction action =
             getTopoCoord().processHeartbeatResponse(
@@ -1594,7 +1594,7 @@ namespace {
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(electedMoreRecentlyResponse),
-                    OpTime(0,0));  // We've never applied anything.
+                    Timestamp(0,0));  // We've never applied anything.
         ASSERT_EQUALS(HeartbeatResponseAction::StepDownRemotePrimary, action.getAction());
         ASSERT_EQUALS(1, action.getPrimaryConfigIndex());
         ASSERT_EQUALS(Date_t(firstRequestDate() + 7000), action.getNextHeartbeatStartDate());
@@ -1607,7 +1607,7 @@ namespace {
         // acknowledge the other member so that we see a majority
         HeartbeatResponseAction action = receiveDownHeartbeat(HostAndPort("host3"),
                                                               "rs0",
-                                                              OpTime(100, 0));
+                                                              Timestamp(100, 0));
         ASSERT_NO_ACTION(action.getAction());
 
         // make us PRIMARY
@@ -1618,7 +1618,7 @@ namespace {
         electedMoreRecentlyResponse.setSetName("rs0");
         electedMoreRecentlyResponse.setState(MemberState::RS_PRIMARY);
         electedMoreRecentlyResponse.setElectable(false);
-        electedMoreRecentlyResponse.setElectionTime(OpTime(10,0));
+        electedMoreRecentlyResponse.setElectionTime(Timestamp(10,0));
         electedMoreRecentlyResponse.setVersion(5);
         action =
             getTopoCoord().processHeartbeatResponse(
@@ -1626,7 +1626,7 @@ namespace {
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(electedMoreRecentlyResponse),
-                    OpTime(0, 0));  // We've never applied anything.
+                    Timestamp(0, 0));  // We've never applied anything.
         ASSERT_EQUALS(HeartbeatResponseAction::StepDownSelf, action.getAction());
         ASSERT_EQUALS(0, action.getPrimaryConfigIndex());
         ASSERT_EQUALS(Date_t(firstRequestDate() + 7000), action.getNextHeartbeatStartDate());
@@ -1644,8 +1644,8 @@ namespace {
         // action.
 
         // acknowledge the other member so that we see a majority
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
         HeartbeatResponseAction action = receiveUpHeartbeat(HostAndPort("host3"),
                                                             "rs0",
                                                             MemberState::RS_SECONDARY,
@@ -1698,7 +1698,7 @@ namespace {
                     target,
                     StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::ExceededTimeLimit,
                                                          "Took too long"),
-                    OpTime(0, 0));  // We've never applied anything.
+                    Timestamp(0, 0));  // We've never applied anything.
 
         ASSERT_EQUALS(HeartbeatResponseAction::NoAction, action.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
@@ -1716,7 +1716,7 @@ namespace {
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::ExceededTimeLimit,
                                                          "Took too long"),
-                    OpTime(0, 0));  // We've never applied anything.
+                    Timestamp(0, 0));  // We've never applied anything.
 
         ASSERT_EQUALS(HeartbeatResponseAction::NoAction, action.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
@@ -1725,8 +1725,8 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataNewPrimary) {
-        OpTime election = OpTime(5,0);
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp election = Timestamp(5,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -1741,9 +1741,9 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataTwoPrimariesNewOneOlder) {
-        OpTime election = OpTime(5,0);
-        OpTime election2 = OpTime(4,0);
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp election = Timestamp(5,0);
+        Timestamp election2 = Timestamp(4,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -1768,9 +1768,9 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataTwoPrimariesNewOneNewer) {
-        OpTime election = OpTime(4,0);
-        OpTime election2 = OpTime(5,0);
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp election = Timestamp(4,0);
+        Timestamp election2 = Timestamp(5,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -1796,10 +1796,10 @@ namespace {
 
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataTwoPrimariesIncludingMeNewOneOlder) {
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
-        makeSelfPrimary(OpTime(5,0));
+        makeSelfPrimary(Timestamp(5,0));
 
-        OpTime election = OpTime(4,0);
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp election = Timestamp(4,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         ASSERT_EQUALS(0, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -1828,9 +1828,9 @@ namespace {
                      0);
         setSelfMemberState(MemberState::RS_SECONDARY);
 
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(13,0);
-        OpTime slightlyLessFreshLastOpTimeApplied = OpTime(3,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(13,0);
+        Timestamp slightlyLessFreshLastOpTimeApplied = Timestamp(3,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -1864,7 +1864,7 @@ namespace {
                               BSON("_id" << 2 << "host" << "host3:27017" << "priority" << 3)) <<
                           "settings" << BSON("heartbeatTimeoutSecs" << 5)),
                      0);
-        OpTime election = OpTime(1000,0);
+        Timestamp election = Timestamp(1000,0);
 
         getTopoCoord().setFollowerMode(MemberState::RS_SECONDARY);
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
@@ -1909,8 +1909,8 @@ namespace {
                               BSON("_id" << 2 << "host" << "host3:27017" << "priority" << 3)) <<
                           "settings" << BSON("heartbeatTimeoutSecs" << 5)),
                      0);
-        OpTime election = OpTime(1000,0);
-        OpTime staleTime = OpTime(0,0);
+        Timestamp election = Timestamp(1000,0);
+        Timestamp staleTime = Timestamp(0,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         makeSelfPrimary(election);
@@ -1938,8 +1938,8 @@ namespace {
                      0);
         setSelfMemberState(MemberState::RS_SECONDARY);
 
-        OpTime election = OpTime(1000,0);
-        OpTime stale = OpTime(0,0);
+        Timestamp election = Timestamp(1000,0);
+        Timestamp stale = Timestamp(0,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -1961,10 +1961,10 @@ namespace {
 
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataTwoPrimariesIncludingMeNewOneNewer) {
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
-        makeSelfPrimary(OpTime(2,0));
+        makeSelfPrimary(Timestamp(2,0));
 
-        OpTime election = OpTime(4,0);
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp election = Timestamp(4,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         ASSERT_EQUALS(0, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -1987,8 +1987,8 @@ namespace {
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataPrimaryDownNoMajority) {
         setSelfMemberState(MemberState::RS_SECONDARY);
 
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -2017,8 +2017,8 @@ namespace {
                               BSON("_id" << 2 << "host" << "host3:27017"))),
                      0);
 
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -2048,8 +2048,8 @@ namespace {
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataPrimaryDownMajorityButIAmStarting) {
         setSelfMemberState(MemberState::RS_STARTUP);
 
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -2078,8 +2078,8 @@ namespace {
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataPrimaryDownMajorityButIAmRecovering) {
         setSelfMemberState(MemberState::RS_RECOVERING);
 
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -2100,8 +2100,8 @@ namespace {
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataPrimaryDownMajorityButIHaveStepdownWait) {
         setSelfMemberState(MemberState::RS_SECONDARY);
 
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -2141,8 +2141,8 @@ namespace {
                               BSON("_id" << 2 << "host" << "host3:27017"))),
                      0);
 
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
 
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host3"),
                                                                 "rs0",
@@ -2171,8 +2171,8 @@ namespace {
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataPrimaryDownMajority) {
         setSelfMemberState(MemberState::RS_SECONDARY);
 
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(399,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(399,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -2215,8 +2215,8 @@ namespace {
         now() += 30000; // we need to be more than LastVote::leaseTime from the start of time or
                         // else some Date_t math goes horribly awry
 
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(130,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(130,0);
         OID round = OID::gen();
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
@@ -2285,9 +2285,9 @@ namespace {
         now() += 30000; // we need to be more than LastVote::leaseTime from the start of time or
                         // else some Date_t math goes horribly awry
 
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(100,0);
-        OpTime fresherOpApplied = OpTime(200,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(100,0);
+        Timestamp fresherOpApplied = Timestamp(200,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -2313,7 +2313,7 @@ namespace {
         ASSERT_EQUALS(HeartbeatResponseAction::StartElection, nextAction.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
 
-        OpTime originalElectionTime = getTopoCoord().getElectionTime();
+        Timestamp originalElectionTime = getTopoCoord().getElectionTime();
         OID originalElectionId = getTopoCoord().getElectionId();
         // prepare an incoming fresh command
         ReplicationCoordinator::ReplSetFreshArgs freshArgs;
@@ -2329,7 +2329,7 @@ namespace {
                 freshArgs, now()++, lastOpTimeApplied, &freshResponseBuilder, &result);
         BSONObj response = freshResponseBuilder.obj();
         ASSERT_OK(result);
-        ASSERT_EQUALS(lastOpTimeApplied, OpTime(response["opTime"].timestampValue()));
+        ASSERT_EQUALS(lastOpTimeApplied, Timestamp(response["opTime"].timestampValue()));
         ASSERT_FALSE(response["fresher"].trueValue());
         ASSERT_FALSE(response["veto"].trueValue());
         ASSERT_TRUE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
@@ -2349,7 +2349,7 @@ namespace {
         result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
         getTopoCoord().prepareElectResponse(
-                electArgs, now()++, OpTime(), &electResponseBuilder, &result);
+                electArgs, now()++, Timestamp(), &electResponseBuilder, &result);
         stopCapturingLogMessages();
         response = electResponseBuilder.obj();
         ASSERT_OK(result);
@@ -2380,7 +2380,7 @@ namespace {
         // now lose election and ensure _electionTime and _electionId are 0'd out 
         getTopoCoord().processLoseElection();
         ASSERT_EQUALS(OID(), getTopoCoord().getElectionId());
-        ASSERT_EQUALS(OpTime(0,0), getTopoCoord().getElectionTime());
+        ASSERT_EQUALS(Timestamp(0,0), getTopoCoord().getElectionTime());
         ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
         ASSERT_EQUALS(2, getCurrentPrimaryIndex());
     }
@@ -2403,9 +2403,9 @@ namespace {
         now() += 30000; // we need to be more than LastVote::leaseTime from the start of time or
                         // else some Date_t math goes horribly awry
 
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(100,0);
-        OpTime fresherLastOpTimeApplied = OpTime(200,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(100,0);
+        Timestamp fresherLastOpTimeApplied = Timestamp(200,0);
         OID round = OID::gen();
         OID remoteRound = OID::gen();
 
@@ -2447,7 +2447,7 @@ namespace {
                 freshArgs, now()++, lastOpTimeApplied, &freshResponseBuilder, &result);
         BSONObj response = freshResponseBuilder.obj();
         ASSERT_OK(result);
-        ASSERT_EQUALS(lastOpTimeApplied, OpTime(response["opTime"].timestampValue()));
+        ASSERT_EQUALS(lastOpTimeApplied, Timestamp(response["opTime"].timestampValue()));
         ASSERT_FALSE(response["fresher"].trueValue());
         ASSERT_FALSE(response["veto"].trueValue());
         ASSERT_TRUE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
@@ -2472,7 +2472,7 @@ namespace {
         result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
         getTopoCoord().prepareElectResponse(
-                electArgs, now()++, OpTime(), &electResponseBuilder, &result);
+                electArgs, now()++, Timestamp(), &electResponseBuilder, &result);
         stopCapturingLogMessages();
         response = electResponseBuilder.obj();
         ASSERT_OK(result);
@@ -2500,9 +2500,9 @@ namespace {
         now() += 30000; // we need to be more than LastVote::leaseTime from the start of time or
                         // else some Date_t math goes horribly awry
 
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(100,0);
-        OpTime fresherLastOpTimeApplied = OpTime(200,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(100,0);
+        Timestamp fresherLastOpTimeApplied = Timestamp(200,0);
         OID round = OID::gen();
         OID remoteRound = OID::gen();
 
@@ -2551,7 +2551,7 @@ namespace {
                 freshArgs, now()++, lastOpTimeApplied, &freshResponseBuilder, &result);
         BSONObj response = freshResponseBuilder.obj();
         ASSERT_OK(result);
-        ASSERT_EQUALS(lastOpTimeApplied, OpTime(response["opTime"].timestampValue()));
+        ASSERT_EQUALS(lastOpTimeApplied, Timestamp(response["opTime"].timestampValue()));
         ASSERT_FALSE(response["fresher"].trueValue());
         ASSERT_TRUE(response["veto"].trueValue()) << response["errmsg"];
         ASSERT_TRUE(TopologyCoordinator::Role::leader == getTopoCoord().getRole());
@@ -2568,7 +2568,7 @@ namespace {
         result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
         getTopoCoord().prepareElectResponse(
-                electArgs, now()++, OpTime(), &electResponseBuilder, &result);
+                electArgs, now()++, Timestamp(), &electResponseBuilder, &result);
         stopCapturingLogMessages();
         response = electResponseBuilder.obj();
         ASSERT_OK(result);
@@ -2594,8 +2594,8 @@ namespace {
 
         setSelfMemberState(MemberState::RS_SECONDARY);
 
-        OpTime election = OpTime(400,0);
-        OpTime lastOpTimeApplied = OpTime(300,0);
+        Timestamp election = Timestamp(400,0);
+        Timestamp lastOpTimeApplied = Timestamp(300,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
@@ -2634,21 +2634,21 @@ namespace {
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataRelinquishPrimaryDueToNodeDisappearing) {
         // become PRIMARY
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
-        makeSelfPrimary(OpTime(2,0));
+        makeSelfPrimary(Timestamp(2,0));
         ASSERT_EQUALS(0, getCurrentPrimaryIndex());
 
         // become aware of other nodes
-        heartbeatFromMember(HostAndPort("host2"), "rs0", MemberState::RS_SECONDARY, OpTime(1,0));
-        heartbeatFromMember(HostAndPort("host2"), "rs0", MemberState::RS_SECONDARY, OpTime(1,0));
-        heartbeatFromMember(HostAndPort("host3"), "rs0", MemberState::RS_SECONDARY, OpTime(0,0));
-        heartbeatFromMember(HostAndPort("host3"), "rs0", MemberState::RS_SECONDARY, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("host2"), "rs0", MemberState::RS_SECONDARY, Timestamp(1,0));
+        heartbeatFromMember(HostAndPort("host2"), "rs0", MemberState::RS_SECONDARY, Timestamp(1,0));
+        heartbeatFromMember(HostAndPort("host3"), "rs0", MemberState::RS_SECONDARY, Timestamp(0,0));
+        heartbeatFromMember(HostAndPort("host3"), "rs0", MemberState::RS_SECONDARY, Timestamp(0,0));
 
         // lose that awareness and be sure we are going to stepdown
         HeartbeatResponseAction nextAction = receiveDownHeartbeat(HostAndPort("host2"),
                                                                   "rs0",
-                                                                  OpTime(100, 0));
+                                                                  Timestamp(100, 0));
         ASSERT_NO_ACTION(nextAction.getAction());
-        nextAction = receiveDownHeartbeat(HostAndPort("host3"), "rs0", OpTime(100, 0));
+        nextAction = receiveDownHeartbeat(HostAndPort("host3"), "rs0", Timestamp(100, 0));
         ASSERT_EQUALS(HeartbeatResponseAction::StepDownSelf, nextAction.getAction());
         ASSERT_EQUALS(0, nextAction.getPrimaryConfigIndex());
         // Doesn't actually do the stepdown until stepDownIfPending is called
@@ -2661,8 +2661,8 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataRemoteDoesNotExist) {
-        OpTime election = OpTime(5,0);
-        OpTime lastOpTimeApplied = OpTime(3,0);
+        Timestamp election = Timestamp(5,0);
+        Timestamp lastOpTimeApplied = Timestamp(3,0);
 
         ASSERT_EQUALS(-1, getCurrentPrimaryIndex());
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host9"),
@@ -2717,7 +2717,7 @@ namespace {
         BSONObjBuilder responseBuilder;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder, &result);
         stopCapturingLogMessages();
         BSONObj response = responseBuilder.obj();
         ASSERT_OK(result);
@@ -2730,7 +2730,7 @@ namespace {
         // Make sure nay votes, do not prevent subsequent yeas (the way a yea vote would)
         args.set = "rs0";
         BSONObjBuilder responseBuilder2;
-        getTopoCoord().prepareElectResponse(args, now++, OpTime(), &responseBuilder2, &result);
+        getTopoCoord().prepareElectResponse(args, now++, Timestamp(), &responseBuilder2, &result);
         BSONObj response2 = responseBuilder2.obj();
         ASSERT_EQUALS(1, response2["vote"].Int());
         ASSERT_EQUALS(round, response2["round"].OID());
@@ -2747,7 +2747,7 @@ namespace {
         BSONObjBuilder responseBuilder;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder, &result);
         stopCapturingLogMessages();
         BSONObj response = responseBuilder.obj();
         ASSERT_OK(result);
@@ -2759,7 +2759,7 @@ namespace {
         // Make sure nay votes, do not prevent subsequent yeas (the way a yea vote would)
         args.cfgver = 10;
         BSONObjBuilder responseBuilder2;
-        getTopoCoord().prepareElectResponse(args, now++, OpTime(), &responseBuilder2, &result);
+        getTopoCoord().prepareElectResponse(args, now++, Timestamp(), &responseBuilder2, &result);
         BSONObj response2 = responseBuilder2.obj();
         ASSERT_EQUALS(1, response2["vote"].Int());
         ASSERT_EQUALS(round, response2["round"].OID());
@@ -2776,7 +2776,7 @@ namespace {
         BSONObjBuilder responseBuilder;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder, &result);
         stopCapturingLogMessages();
         BSONObj response = responseBuilder.obj();
         ASSERT_OK(result);
@@ -2788,7 +2788,7 @@ namespace {
         // Make sure nay votes, do not prevent subsequent yeas (the way a yea vote would)
         args.cfgver = 10;
         BSONObjBuilder responseBuilder2;
-        getTopoCoord().prepareElectResponse(args, now++, OpTime(), &responseBuilder2, &result);
+        getTopoCoord().prepareElectResponse(args, now++, Timestamp(), &responseBuilder2, &result);
         BSONObj response2 = responseBuilder2.obj();
         ASSERT_EQUALS(1, response2["vote"].Int());
         ASSERT_EQUALS(round, response2["round"].OID());
@@ -2805,7 +2805,7 @@ namespace {
         BSONObjBuilder responseBuilder;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder, &result);
         stopCapturingLogMessages();
         BSONObj response = responseBuilder.obj();
         ASSERT_OK(result);
@@ -2816,7 +2816,7 @@ namespace {
         // Make sure nay votes, do not prevent subsequent yeas (the way a yea vote would)
         args.whoid = 1;
         BSONObjBuilder responseBuilder2;
-        getTopoCoord().prepareElectResponse(args, now++, OpTime(), &responseBuilder2, &result);
+        getTopoCoord().prepareElectResponse(args, now++, Timestamp(), &responseBuilder2, &result);
         BSONObj response2 = responseBuilder2.obj();
         ASSERT_EQUALS(1, response2["vote"].Int());
         ASSERT_EQUALS(round, response2["round"].OID());
@@ -2835,7 +2835,7 @@ namespace {
         BSONObjBuilder responseBuilder;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder, &result);
         stopCapturingLogMessages();
         BSONObj response = responseBuilder.obj();
         ASSERT_OK(result);
@@ -2846,7 +2846,7 @@ namespace {
         // Make sure nay votes, do not prevent subsequent yeas (the way a yea vote would)
         getTopoCoord()._setCurrentPrimaryForTest(-1);
         BSONObjBuilder responseBuilder2;
-        getTopoCoord().prepareElectResponse(args, now++, OpTime(), &responseBuilder2, &result);
+        getTopoCoord().prepareElectResponse(args, now++, Timestamp(), &responseBuilder2, &result);
         BSONObj response2 = responseBuilder2.obj();
         ASSERT_EQUALS(1, response2["vote"].Int());
         ASSERT_EQUALS(round, response2["round"].OID());
@@ -2864,7 +2864,7 @@ namespace {
         BSONObjBuilder responseBuilder;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder, &result);
         stopCapturingLogMessages();
         BSONObj response = responseBuilder.obj();
         ASSERT_OK(result);
@@ -2875,7 +2875,7 @@ namespace {
         // Make sure nay votes, do not prevent subsequent yeas (the way a yea vote would)
         getTopoCoord()._setCurrentPrimaryForTest(-1);
         BSONObjBuilder responseBuilder2;
-        getTopoCoord().prepareElectResponse(args, now++, OpTime(), &responseBuilder2, &result);
+        getTopoCoord().prepareElectResponse(args, now++, Timestamp(), &responseBuilder2, &result);
         BSONObj response2 = responseBuilder2.obj();
         ASSERT_EQUALS(1, response2["vote"].Int());
         ASSERT_EQUALS(round, response2["round"].OID());
@@ -2894,7 +2894,7 @@ namespace {
         BSONObjBuilder responseBuilder;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder, &result);
         stopCapturingLogMessages();
         BSONObj response = responseBuilder.obj();
         ASSERT_OK(result);
@@ -2905,7 +2905,7 @@ namespace {
         // Make sure nay votes, do not prevent subsequent yeas (the way a yea vote would)
         args.whoid = 3;
         BSONObjBuilder responseBuilder2;
-        getTopoCoord().prepareElectResponse(args, now++, OpTime(), &responseBuilder2, &result);
+        getTopoCoord().prepareElectResponse(args, now++, Timestamp(), &responseBuilder2, &result);
         BSONObj response2 = responseBuilder2.obj();
         ASSERT_EQUALS(1, response2["vote"].Int());
         ASSERT_EQUALS(round, response2["round"].OID());
@@ -2920,13 +2920,13 @@ namespace {
         args.cfgver = 10;
         args.whoid = 1;
 
-        receiveDownHeartbeat(HostAndPort("h3"), "rs0", OpTime());
-        receiveDownHeartbeat(HostAndPort("h2"), "rs0", OpTime());
+        receiveDownHeartbeat(HostAndPort("h3"), "rs0", Timestamp());
+        receiveDownHeartbeat(HostAndPort("h2"), "rs0", Timestamp());
 
         BSONObjBuilder responseBuilder;
         Status result = Status::OK();
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder, &result);
         stopCapturingLogMessages();
         BSONObj response = responseBuilder.obj();
         ASSERT_EQUALS(1, response["vote"].Int());
@@ -2945,7 +2945,7 @@ namespace {
         BSONObjBuilder responseBuilder1;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now += 60000, OpTime(), &responseBuilder1, &result);
+        getTopoCoord().prepareElectResponse(args, now += 60000, Timestamp(), &responseBuilder1, &result);
         stopCapturingLogMessages();
         BSONObj response1 = responseBuilder1.obj();
         ASSERT_OK(result);
@@ -2958,7 +2958,7 @@ namespace {
 
         BSONObjBuilder responseBuilder2;
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now, OpTime(), &responseBuilder2, &result);
+        getTopoCoord().prepareElectResponse(args, now, Timestamp(), &responseBuilder2, &result);
         stopCapturingLogMessages();
         BSONObj response2 = responseBuilder2.obj();
         ASSERT_OK(result);
@@ -2972,7 +2972,7 @@ namespace {
 
         BSONObjBuilder responseBuilder3;
         startCapturingLogMessages();
-        getTopoCoord().prepareElectResponse(args, now++, OpTime(), &responseBuilder3, &result);
+        getTopoCoord().prepareElectResponse(args, now++, Timestamp(), &responseBuilder3, &result);
         stopCapturingLogMessages();
         BSONObj response3 = responseBuilder3.obj();
         ASSERT_OK(result);
@@ -2985,7 +2985,7 @@ namespace {
         ReplicationCoordinator::ReplSetElectArgs args;
         BSONObjBuilder response;
         Status status = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
-        getTopoCoord().prepareElectResponse(args, now(), OpTime(), &response, &status);
+        getTopoCoord().prepareElectResponse(args, now(), Timestamp(), &response, &status);
         ASSERT_EQUALS(ErrorCodes::ReplicaSetNotFound, status);
         ASSERT_EQUALS("Cannot participate in election because not initialized", status.reason());
     }
@@ -3102,7 +3102,7 @@ namespace {
         BSONObjBuilder response;
         getTopoCoord().prepareSyncFromResponse(cbData(),
                                                HostAndPort("host2:27017"),
-                                               OpTime(0,0),
+                                               Timestamp(0,0),
                                                &response,
                                                &result);
         ASSERT_EQUALS(ErrorCodes::ShutdownInProgress, result);
@@ -3116,7 +3116,7 @@ namespace {
         getTopoCoord().prepareStatusResponse(cbData(),
                                              Date_t(0),
                                              0,
-                                             OpTime(0,0),
+                                             Timestamp(0,0),
                                              &response,
                                              &result);
         ASSERT_EQUALS(ErrorCodes::ShutdownInProgress, result);
@@ -3139,7 +3139,7 @@ namespace {
         }
 
         void prepareHeartbeatResponse(const ReplSetHeartbeatArgs& args,
-                                      OpTime lastOpApplied,
+                                      Timestamp lastOpApplied,
                                       ReplSetHeartbeatResponse* response,
                                       Status* result) {
             *result = getTopoCoord().prepareHeartbeatResponse(now()++,
@@ -3159,7 +3159,7 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(0,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(0,0), &response, &result);
         ASSERT_EQUALS(ErrorCodes::BadValue, result);
         ASSERT_EQUALS("replset: incompatible replset protocol version: 3", result.reason());
         ASSERT_EQUALS("", response.getHbMsg());
@@ -3173,7 +3173,7 @@ namespace {
         args.setSenderId(10);
         ReplSetHeartbeatResponse response;
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
-        prepareHeartbeatResponse(args, OpTime(0,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(0,0), &response, &result);
         ASSERT_EQUALS(ErrorCodes::BadValue, result);
         ASSERT(result.reason().find("from member with the same member ID as our self")) <<
                 "Actual string was \"" << result.reason() << '"';
@@ -3189,7 +3189,7 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         startCapturingLogMessages();
-        prepareHeartbeatResponse(args, OpTime(0,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(0,0), &response, &result);
         stopCapturingLogMessages();
         ASSERT_EQUALS(ErrorCodes::InconsistentReplicaSetNames, result);
         ASSERT(result.reason().find("repl set names do not match")) << "Actual string was \"" <<
@@ -3211,12 +3211,12 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(0,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(0,0), &response, &result);
         ASSERT_OK(result);
         ASSERT_FALSE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
-        ASSERT_EQUALS(OpTime(0,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
@@ -3234,12 +3234,12 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(0,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(0,0), &response, &result);
         ASSERT_OK(result);
         ASSERT_FALSE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
-        ASSERT_EQUALS(OpTime(0,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
@@ -3257,13 +3257,13 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(0,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(0,0), &response, &result);
         ASSERT_OK(result);
         ASSERT_TRUE(response.hasConfig());
         ASSERT_FALSE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
-        ASSERT_EQUALS(OpTime(0,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
@@ -3281,13 +3281,13 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(0,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(0,0), &response, &result);
         ASSERT_OK(result);
         ASSERT_FALSE(response.hasConfig());
         ASSERT_FALSE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
-        ASSERT_EQUALS(OpTime(0,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
@@ -3305,12 +3305,12 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(0,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(0,0), &response, &result);
         ASSERT_OK(result);
         ASSERT_FALSE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
-        ASSERT_EQUALS(OpTime(0,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
@@ -3320,7 +3320,7 @@ namespace {
 
     TEST_F(PrepareHeartbeatResponseTest, PrepareHeartbeatResponseSenderUp) {
         // set up args and acknowledge sender
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, Timestamp(0,0));
         ReplSetHeartbeatArgs args;
         args.setProtocolVersion(1);
         args.setConfigVersion(1);
@@ -3330,13 +3330,13 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(100,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(100,0), &response, &result);
         ASSERT_OK(result);
         // this change to true because we can now see a majority, unlike in the previous cases
         ASSERT_TRUE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
-        ASSERT_EQUALS(OpTime(100,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(100,0), response.getOpTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
@@ -3355,14 +3355,14 @@ namespace {
         Status result = getTopoCoord().prepareHeartbeatResponse(now()++,
                                                                 args,
                                                                 "rs0",
-                                                                OpTime(0,0),
+                                                                Timestamp(0,0),
                                                                 &response);
         ASSERT_OK(result);
         // this change to true because we can now see a majority, unlike in the previous cases
         ASSERT_FALSE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_STARTUP, response.getState().s);
-        ASSERT_EQUALS(OpTime(0,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("", response.getReplicaSetName());
@@ -3370,8 +3370,8 @@ namespace {
     }
 
     TEST_F(PrepareHeartbeatResponseTest, PrepareHeartbeatResponseAsPrimary) {
-        makeSelfPrimary(OpTime(10,0));
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, OpTime(0,0));
+        makeSelfPrimary(Timestamp(10,0));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, Timestamp(0,0));
 
         ReplSetHeartbeatArgs args;
         args.setProtocolVersion(1);
@@ -3382,14 +3382,14 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(11,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(11,0), &response, &result);
         ASSERT_OK(result);
         // electable because we are already primary
         ASSERT_TRUE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_PRIMARY, response.getState().s);
-        ASSERT_EQUALS(OpTime(11,0), response.getOpTime());
-        ASSERT_EQUALS(OpTime(10,0), response.getElectionTime());
+        ASSERT_EQUALS(Timestamp(11,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(10,0), response.getElectionTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
@@ -3398,11 +3398,11 @@ namespace {
 
     TEST_F(PrepareHeartbeatResponseTest, PrepareHeartbeatResponseWithSyncSource) {
         // get a sync source
-        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, OpTime(0,0));
-        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, OpTime(0,0));
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, OpTime(1,0));
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, OpTime(1,0));
-        getTopoCoord().chooseNewSyncSource(now()++, OpTime(0,0));
+        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, Timestamp(0,0));
+        heartbeatFromMember(HostAndPort("h3"), "rs0", MemberState::RS_SECONDARY, Timestamp(0,0));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, Timestamp(1,0));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, Timestamp(1,0));
+        getTopoCoord().chooseNewSyncSource(now()++, Timestamp(0,0));
 
         // set up args
         ReplSetHeartbeatArgs args;
@@ -3414,12 +3414,12 @@ namespace {
         Status result(ErrorCodes::InternalError, "prepareHeartbeatResponse didn't set result");
 
         // prepare response and check the results
-        prepareHeartbeatResponse(args, OpTime(100,0), &response, &result);
+        prepareHeartbeatResponse(args, Timestamp(100,0), &response, &result);
         ASSERT_OK(result);
         ASSERT_TRUE(response.isElectable());
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
-        ASSERT_EQUALS(OpTime(100,0), response.getOpTime());
+        ASSERT_EQUALS(Timestamp(100,0), response.getOpTime());
         ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
         // changed to a syncing message because our sync source changed recently
         ASSERT_EQUALS("syncing from: h2:27017", response.getHbMsg());
@@ -3453,7 +3453,7 @@ namespace {
                             "version" << 1 <<
                             "members" << BSON_ARRAY(
                                 BSON("_id" << 1 << "host" << "hself" << "priority" << 0))));
-        getTopoCoord().updateConfig(cfg, 0, now()++, OpTime());
+        getTopoCoord().updateConfig(cfg, 0, now()++, Timestamp());
         ASSERT_EQUALS(MemberState::RS_STARTUP2, getTopoCoord().getMemberState().s);
 
         ASSERT_FALSE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
@@ -3480,7 +3480,7 @@ namespace {
                             "members" << BSON_ARRAY(
                                 BSON("_id" << 1 << "host" << "hself" << "priority" << 0))));
 
-        getTopoCoord().updateConfig(cfg, 0, now()++, OpTime());
+        getTopoCoord().updateConfig(cfg, 0, now()++, Timestamp());
         ASSERT_EQUALS(MemberState::RS_STARTUP2, getTopoCoord().getMemberState().s);
 
         // despite being the only node, we are unelectable, so we should not become a candidate
@@ -3556,7 +3556,7 @@ namespace {
         ASSERT_TRUE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
 
         // win election and primary
-        getTopoCoord().processWinElection(OID::gen(), OpTime(0,0));
+        getTopoCoord().processWinElection(OID::gen(), Timestamp(0,0));
         ASSERT_TRUE(TopologyCoordinator::Role::leader == getTopoCoord().getRole());
         ASSERT_EQUALS(MemberState::RS_PRIMARY, getTopoCoord().getMemberState().s);
 
@@ -3586,7 +3586,7 @@ namespace {
         ASSERT_TRUE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
 
         // win election and primary
-        getTopoCoord().processWinElection(OID::gen(), OpTime(0,0));
+        getTopoCoord().processWinElection(OID::gen(), Timestamp(0,0));
         ASSERT_TRUE(TopologyCoordinator::Role::leader == getTopoCoord().getRole());
         ASSERT_EQUALS(MemberState::RS_PRIMARY, getTopoCoord().getMemberState().s);
 
@@ -3617,7 +3617,7 @@ namespace {
          ASSERT_TRUE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
 
          // win election and primary
-         getTopoCoord().processWinElection(OID::gen(), OpTime(0,0));
+         getTopoCoord().processWinElection(OID::gen(), Timestamp(0,0));
          ASSERT_TRUE(TopologyCoordinator::Role::leader == getTopoCoord().getRole());
          ASSERT_EQUALS(MemberState::RS_PRIMARY, getTopoCoord().getMemberState().s);
 
@@ -3631,7 +3631,7 @@ namespace {
                                BSON("_id" << 2 << "host" << "host3:27017"))),
                       0,
                       Date_t(-1),
-                      OpTime(10,0));
+                      Timestamp(10,0));
          ASSERT_TRUE(TopologyCoordinator::Role::leader == getTopoCoord().getRole());
          ASSERT_EQUALS(MemberState::RS_PRIMARY, getTopoCoord().getMemberState().s);
 
@@ -3646,7 +3646,7 @@ namespace {
                                     "tags" <<  BSON("dc" << "NA" << "rack" << "rack1")))),
                       0,
                       Date_t(-1),
-                      OpTime(10,0));
+                      Timestamp(10,0));
          ASSERT_TRUE(TopologyCoordinator::Role::leader == getTopoCoord().getRole());
          ASSERT_EQUALS(MemberState::RS_PRIMARY, getTopoCoord().getMemberState().s);
      }
@@ -3676,8 +3676,8 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseTest, ReconfigBetweenHeartbeatRequestAndRepsonse) {
-        OpTime election = OpTime(14,0);
-        OpTime lastOpTimeApplied = OpTime(13,0);
+        Timestamp election = Timestamp(14,0);
+        Timestamp lastOpTimeApplied = Timestamp(13,0);
 
         // all three members up and secondaries
         setSelfMemberState(MemberState::RS_SECONDARY);
@@ -3727,8 +3727,8 @@ namespace {
     }
 
     TEST_F(HeartbeatResponseTest, ReconfigNodeRemovedBetweenHeartbeatRequestAndRepsonse) {
-        OpTime election = OpTime(14,0);
-        OpTime lastOpTimeApplied = OpTime(13,0);
+        Timestamp election = Timestamp(14,0);
+        Timestamp lastOpTimeApplied = Timestamp(13,0);
 
         // all three members up and secondaries
         setSelfMemberState(MemberState::RS_SECONDARY);
@@ -3793,10 +3793,10 @@ namespace {
     TEST_F(HeartbeatResponseTest, ShouldChangeSyncSourceFresherHappierMemberExists) {
         // In this test, the TopologyCoordinator should tell us to change sync sources away from 
         // "host2" and to "host3" since "host2" is more than maxSyncSourceLagSecs(30) behind "host3"
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(4,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(4,0);
         // ahead by more than maxSyncSourceLagSecs (30)
-        OpTime fresherLastOpTimeApplied = OpTime(3005,0);
+        Timestamp fresherLastOpTimeApplied = Timestamp(3005,0);
 
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
                                                                 "rs0",
@@ -3826,10 +3826,10 @@ namespace {
         // "host2" and to "host3" despite "host2" being more than maxSyncSourceLagSecs(30) behind
         // "host3", since "host3" is blacklisted
         // Then, confirm that unblacklisting only works if time has passed the blacklist time.
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(400,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(400,0);
         // ahead by more than maxSyncSourceLagSecs (30)
-        OpTime fresherLastOpTimeApplied = OpTime(3005,0);
+        Timestamp fresherLastOpTimeApplied = Timestamp(3005,0);
 
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
                                                                 "rs0",
@@ -3867,10 +3867,10 @@ namespace {
         // In this test, the TopologyCoordinator should not tell us to change sync sources away from 
         // "host2" and to "host3" despite "host2" being more than maxSyncSourceLagSecs(30) behind
         // "host3", since "host3" is down
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(400,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(400,0);
         // ahead by more than maxSyncSourceLagSecs (30)
-        OpTime fresherLastOpTimeApplied = OpTime(3005,0);
+        Timestamp fresherLastOpTimeApplied = Timestamp(3005,0);
 
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
                                                                 "rs0",
@@ -3898,10 +3898,10 @@ namespace {
         // In this test, the TopologyCoordinator should not tell us to change sync sources away from 
         // "host2" and to "host3" despite "host2" being more than maxSyncSourceLagSecs(30) behind
         // "host3", since "host3" is in a non-readable mode (RS_ROLLBACK)
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(4,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(4,0);
         // ahead by more than maxSyncSourceLagSecs (30)
-        OpTime fresherLastOpTimeApplied = OpTime(3005,0);
+        Timestamp fresherLastOpTimeApplied = Timestamp(3005,0);
 
         HeartbeatResponseAction nextAction = receiveUpHeartbeat(HostAndPort("host2"),
                                                                 "rs0",
@@ -3927,10 +3927,10 @@ namespace {
         // In this test, the TopologyCoordinator should not tell us to change sync sources away from 
         // "host2" and to "host3" despite "host2" being more than maxSyncSourceLagSecs(30) behind
         // "host3", since "host3" does not build indexes
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(4,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(4,0);
         // ahead by more than maxSyncSourceLagSecs (30)
-        OpTime fresherLastOpTimeApplied = OpTime(3005,0);
+        Timestamp fresherLastOpTimeApplied = Timestamp(3005,0);
 
         updateConfig(BSON("_id" << "rs0" <<
                           "version" << 6 <<
@@ -3963,10 +3963,10 @@ namespace {
         // In this test, the TopologyCoordinator should tell us to change sync sources away from 
         // "host2" and to "host3" despite "host3" not building indexes because we do not build
         // indexes either and "host2" is more than maxSyncSourceLagSecs(30) behind "host3"
-        OpTime election = OpTime(0,0);
-        OpTime lastOpTimeApplied = OpTime(4,0);
+        Timestamp election = Timestamp(0,0);
+        Timestamp lastOpTimeApplied = Timestamp(4,0);
         // ahead by more than maxSyncSourceLagSecs (30)
-        OpTime fresherLastOpTimeApplied = OpTime(3005,0);
+        Timestamp fresherLastOpTimeApplied = Timestamp(3005,0);
 
         updateConfig(BSON("_id" << "rs0" <<
                           "version" << 7 <<
@@ -4009,8 +4009,8 @@ namespace {
                      0);
         setSelfMemberState(MemberState::RS_SECONDARY);
 
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_PRIMARY, OpTime(1,0));
-        ASSERT_FALSE(getTopoCoord().checkShouldStandForElection(now()++, OpTime(0,0)));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_PRIMARY, Timestamp(1,0));
+        ASSERT_FALSE(getTopoCoord().checkShouldStandForElection(now()++, Timestamp(0,0)));
     }
 
     TEST_F(TopoCoordTest, CheckShouldStandForElectionNotCloseEnoughToLastOptime) {
@@ -4023,8 +4023,8 @@ namespace {
                      0);
         setSelfMemberState(MemberState::RS_SECONDARY);
 
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, OpTime(10000,0));
-        ASSERT_FALSE(getTopoCoord().checkShouldStandForElection(now()++, OpTime(100,0)));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, Timestamp(10000,0));
+        ASSERT_FALSE(getTopoCoord().checkShouldStandForElection(now()++, Timestamp(100,0)));
     }
 
     TEST_F(TopoCoordTest, VoteForMyselfFailsWhileNotCandidate) {
@@ -4053,7 +4053,7 @@ namespace {
     TEST_F(TopoCoordTest, UnelectableIfAbsentFromConfig) {
         logger::globalLogDomain()->setMinimumLoggedSeverity(logger::LogSeverity::Debug(3));
         startCapturingLogMessages();
-        ASSERT_FALSE(getTopoCoord().checkShouldStandForElection(now()++, OpTime(10,0)));
+        ASSERT_FALSE(getTopoCoord().checkShouldStandForElection(now()++, Timestamp(10,0)));
         stopCapturingLogMessages();
         ASSERT_EQUALS(1, countLogLinesContaining("not a member of a valid replica set config"));
         logger::globalLogDomain()->setMinimumLoggedSeverity(logger::LogSeverity::Log());
@@ -4068,7 +4068,7 @@ namespace {
                               BSON("_id" << 30 << "host" << "h3"))),
                      0);
         setSelfMemberState(MemberState::RS_SECONDARY);
-        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, OpTime(100,0));
+        heartbeatFromMember(HostAndPort("h2"), "rs0", MemberState::RS_SECONDARY, Timestamp(100,0));
 
         // vote for another node
         OID remoteRound = OID::gen();
@@ -4083,7 +4083,7 @@ namespace {
         BSONObjBuilder electResponseBuilder;
         Status result = Status(ErrorCodes::InternalError, "status not set by prepareElectResponse");
         getTopoCoord().prepareElectResponse(
-                electArgs, now()++, OpTime(100,0), &electResponseBuilder, &result);
+                electArgs, now()++, Timestamp(100,0), &electResponseBuilder, &result);
         BSONObj response = electResponseBuilder.obj();
         ASSERT_OK(result);
         std::cout << response;
@@ -4092,7 +4092,7 @@ namespace {
 
         logger::globalLogDomain()->setMinimumLoggedSeverity(logger::LogSeverity::Debug(3));
         startCapturingLogMessages();
-        ASSERT_FALSE(getTopoCoord().checkShouldStandForElection(now()++, OpTime(10,0)));
+        ASSERT_FALSE(getTopoCoord().checkShouldStandForElection(now()++, Timestamp(10,0)));
         stopCapturingLogMessages();
         ASSERT_EQUALS(1, countLogLinesContaining("I recently voted for "));
         logger::globalLogDomain()->setMinimumLoggedSeverity(logger::LogSeverity::Log());
diff --git a/src/mongo/db/repl/update_position_args.cpp b/src/mongo/db/repl/update_position_args.cpp
index 78b08bfc483..39b0aa762f9 100644
--- a/src/mongo/db/repl/update_position_args.cpp
+++ b/src/mongo/db/repl/update_position_args.cpp
@@ -40,7 +40,7 @@ namespace repl {
 
 
     UpdatePositionArgs::UpdateInfo::UpdateInfo(
-            const OID& anRid, const OpTime& aTs, long long aCfgver, long long aMemberId)
+            const OID& anRid, const Timestamp& aTs, long long aCfgver, long long aMemberId)
         : rid(anRid), ts(aTs), cfgver(aCfgver), memberId(aMemberId) {}
 
 namespace {
@@ -93,8 +93,8 @@ namespace {
             if (!status.isOK())
                 return status;
 
-            OpTime ts;
-            status = bsonExtractOpTimeField(entry, kOpTimeFieldName, &ts);
+            Timestamp ts;
+            status = bsonExtractTimestampField(entry, kOpTimeFieldName, &ts);
             if (!status.isOK())
                 return status;
 
diff --git a/src/mongo/db/repl/update_position_args.h b/src/mongo/db/repl/update_position_args.h
index 9d9afebced2..e0fb6ebf805 100644
--- a/src/mongo/db/repl/update_position_args.h
+++ b/src/mongo/db/repl/update_position_args.h
@@ -44,10 +44,10 @@ namespace repl {
     class UpdatePositionArgs {
     public:
         struct UpdateInfo {
-            UpdateInfo(const OID& anRid, const OpTime& aTs, long long aCfgver, long long aMemberId);
+            UpdateInfo(const OID& anRid, const Timestamp& aTs, long long aCfgver, long long aMemberId);
 
             OID rid;
-            OpTime ts;
+            Timestamp ts;
             long long cfgver;
             long long memberId;
         };
diff --git a/src/mongo/db/storage/index_entry_comparison.h b/src/mongo/db/storage/index_entry_comparison.h
index f12ea85c4f2..c1415c2fba2 100644
--- a/src/mongo/db/storage/index_entry_comparison.h
+++ b/src/mongo/db/storage/index_entry_comparison.h
@@ -30,9 +30,7 @@
 
 #include <vector>
 
-#include "mongo/bson/bsonelement.h"
-#include "mongo/bson/bsonobj.h"
-#include "mongo/bson/ordering.h"
+#include "mongo/db/jsobj.h"
 #include "mongo/db/record_id.h"
 
 namespace mongo {
diff --git a/src/mongo/db/storage/key_string.cpp b/src/mongo/db/storage/key_string.cpp
index 13e7711a217..2b3391e1d42 100644
--- a/src/mongo/db/storage/key_string.cpp
+++ b/src/mongo/db/storage/key_string.cpp
@@ -143,7 +143,7 @@ namespace mongo {
             case jstOID: return CType::kOID;
             case Bool: return CType::kBool;
             case Date: return CType::kDate;
-            case Timestamp: return CType::kTimestamp;
+            case bsonTimestamp: return CType::kTimestamp;
             case RegEx: return CType::kRegEx;
             case DBRef: return CType::kDBRef;
 
@@ -363,7 +363,7 @@ namespace mongo {
         _append(endian::nativeToBig(encoded), invert);
     }
 
-    void KeyString::_appendTimestamp(OpTime val, bool invert) {
+    void KeyString::_appendTimestamp(Timestamp val, bool invert) {
         _append(CType::kTimestamp, invert);
         _append(endian::nativeToBig(val.asLL()), invert);
     }
@@ -558,7 +558,7 @@ namespace mongo {
             break;
         }
         case NumberInt: _appendNumberInt(elem._numberInt(), invert); break;
-        case Timestamp: _appendTimestamp(elem._opTime(), invert); break;
+        case bsonTimestamp: _appendTimestamp(elem.timestamp(), invert); break;
         case NumberLong: _appendNumberLong(elem._numberLong(), invert); break;
 
         default:
@@ -740,7 +740,7 @@ namespace mongo {
                 break;
 
             case CType::kTimestamp:
-                *stream << OpTime(endian::bigToNative(readType<uint64_t>(reader, inverted)));
+                *stream << Timestamp(endian::bigToNative(readType<uint64_t>(reader, inverted)));
                 break;
 
             case CType::kOID:
diff --git a/src/mongo/db/storage/key_string.h b/src/mongo/db/storage/key_string.h
index 50b05141818..5bd9cf7c8a9 100644
--- a/src/mongo/db/storage/key_string.h
+++ b/src/mongo/db/storage/key_string.h
@@ -31,9 +31,8 @@
 #include "mongo/bson/bsonobj.h"
 #include "mongo/bson/bsonobjbuilder.h"
 #include "mongo/bson/bsonmisc.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/bson/ordering.h"
-#include "mongo/bson/bson_db.h"
 #include "mongo/db/record_id.h"
 
 namespace mongo {
@@ -248,7 +247,7 @@ namespace mongo {
 
         void _appendBool(bool val, bool invert);
         void _appendDate(Date_t val, bool invert);
-        void _appendTimestamp(OpTime val, bool invert);
+        void _appendTimestamp(Timestamp val, bool invert);
         void _appendOID(OID val, bool invert);
         void _appendString(StringData val, bool invert);
         void _appendSymbol(StringData val, bool invert);
diff --git a/src/mongo/db/storage/key_string_test.cpp b/src/mongo/db/storage/key_string_test.cpp
index 5d122844aeb..267f1ba6501 100644
--- a/src/mongo/db/storage/key_string_test.cpp
+++ b/src/mongo/db/storage/key_string_test.cpp
@@ -150,7 +150,7 @@ TEST(KeyStringTest, AllTypesSimple) {
     ROUNDTRIP(BSON("" << BSONCode("abc_code")));
     ROUNDTRIP(BSON("" << BSONCodeWScope("def_code", BSON("x_scope" << "a"))));
     ROUNDTRIP(BSON("" << 5));
-    ROUNDTRIP(BSON("" << OpTime(123123, 123)));
+    ROUNDTRIP(BSON("" << Timestamp(123123, 123)));
     ROUNDTRIP(BSON("" << 1235123123123LL));
 }
 
@@ -310,12 +310,12 @@ TEST(KeyStringTest, RecordIdOrder2Double) {
     ASSERT_LESS_THAN(a, c);
 }
 
-TEST(KeyStringTest, OpTime) {
+TEST(KeyStringTest, Timestamp) {
 
-    BSONObj a = BSON("" << OpTime(0, 0));
-    BSONObj b = BSON("" << OpTime(1234, 1));
-    BSONObj c = BSON("" << OpTime(1234, 2));
-    BSONObj d = BSON("" << OpTime(1235, 1));
+    BSONObj a = BSON("" << Timestamp(0, 0));
+    BSONObj b = BSON("" << Timestamp(1234, 1));
+    BSONObj c = BSON("" << Timestamp(1234, 2));
+    BSONObj d = BSON("" << Timestamp(1235, 1));
 
     {
         ROUNDTRIP(a);
diff --git a/src/mongo/db/storage/mmap_v1/btree/key.cpp b/src/mongo/db/storage/mmap_v1/btree/key.cpp
index 0ee18f614ac..c49e944ceb3 100644
--- a/src/mongo/db/storage/mmap_v1/btree/key.cpp
+++ b/src/mongo/db/storage/mmap_v1/btree/key.cpp
@@ -65,7 +65,7 @@ namespace mongo {
             return 0;
         case Bool:
             return *l.value() - *r.value();
-        case Timestamp:
+        case bsonTimestamp:
         case Date:
             // unsigned dates for old version
             if ( l.date() < r.date() )
diff --git a/src/mongo/db/storage/mmap_v1/dur_preplogbuffer.cpp b/src/mongo/db/storage/mmap_v1/dur_preplogbuffer.cpp
index 1a0d03d96a4..73583a77ef7 100644
--- a/src/mongo/db/storage/mmap_v1/dur_preplogbuffer.cpp
+++ b/src/mongo/db/storage/mmap_v1/dur_preplogbuffer.cpp
@@ -39,6 +39,7 @@
 #include "mongo/platform/basic.h"
 
 #include <boost/shared_ptr.hpp>
+#include <boost/thread.hpp>
 
 #include "mongo/db/storage/mmap_v1/aligned_builder.h"
 #include "mongo/db/storage/mmap_v1/durable_mapped_file.h"
diff --git a/src/mongo/db/storage/oplog_hack.cpp b/src/mongo/db/storage/oplog_hack.cpp
index 0bee74310f7..b25268e4271 100644
--- a/src/mongo/db/storage/oplog_hack.cpp
+++ b/src/mongo/db/storage/oplog_hack.cpp
@@ -34,7 +34,7 @@
 #include <limits>
 
 #include "mongo/bson/bson_validate.h"
-#include "mongo/bson/optime.h"
+#include "mongo/bson/timestamp.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/db/record_id.h"
 #include "mongo/util/debug_util.h"
@@ -42,7 +42,7 @@
 namespace mongo {
 namespace oploghack {
 
-    StatusWith<RecordId> keyForOptime(const OpTime& opTime) {
+    StatusWith<RecordId> keyForOptime(const Timestamp& opTime) {
         // Make sure secs and inc wouldn't be negative if treated as signed. This ensures that they
         // don't sort differently when put in a RecordId. It also avoids issues with Null/Invalid
         // RecordIds
@@ -71,10 +71,10 @@ namespace oploghack {
         const BSONElement elem = obj["ts"];
         if (elem.eoo())
             return StatusWith<RecordId>(ErrorCodes::BadValue, "no ts field");
-        if (elem.type() != Timestamp)
+        if (elem.type() != bsonTimestamp)
             return StatusWith<RecordId>(ErrorCodes::BadValue, "ts must be a Timestamp");
 
-        return keyForOptime(elem._opTime());
+        return keyForOptime(elem.timestamp());
     }
 
 }  // namespace oploghack
diff --git a/src/mongo/db/storage/oplog_hack.h b/src/mongo/db/storage/oplog_hack.h
index 20708c1db4c..92138959304 100644
--- a/src/mongo/db/storage/oplog_hack.h
+++ b/src/mongo/db/storage/oplog_hack.h
@@ -33,15 +33,15 @@
 
 namespace mongo {
     class RecordId;
-    class OpTime;
+    class Timestamp;
 
 namespace oploghack {
 
     /**
-     * Converts OpTime to a RecordId in an unspecified manor that is safe to use as the key to in a
-     * RecordStore.
+     * Converts Timestamp to a RecordId in an unspecified manor that is safe to use as the key to
+     * in a RecordStore.
      */
-    StatusWith<RecordId> keyForOptime(const OpTime& opTime);
+    StatusWith<RecordId> keyForOptime(const Timestamp& opTime);
 
     /**
      * data and len must be the arguments from RecordStore::insert() on an oplog collection.
diff --git a/src/mongo/db/storage/record_store.h b/src/mongo/db/storage/record_store.h
index 48e5aec5e06..f0a09eb67fd 100644
--- a/src/mongo/db/storage/record_store.h
+++ b/src/mongo/db/storage/record_store.h
@@ -343,7 +343,7 @@ namespace mongo {
          * they are ordered.
          */
         virtual Status oplogDiskLocRegister( OperationContext* txn,
-                                             const OpTime& opTime ) {
+                                             const Timestamp& opTime ) {
             return Status::OK();
         }
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
index ee440b67216..c53686fa623 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
@@ -863,7 +863,7 @@ namespace {
     }
 
     Status WiredTigerRecordStore::oplogDiskLocRegister( OperationContext* txn,
-                                                        const OpTime& opTime ) {
+                                                        const Timestamp& opTime ) {
         StatusWith<RecordId> loc = oploghack::keyForOptime( opTime );
         if ( !loc.isOK() )
             return loc.getStatus();
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.h b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.h
index 6defe3552fa..5447425ca9b 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.h
@@ -182,7 +182,7 @@ namespace mongo {
                                                          const RecordId& startingPosition) const;
 
         virtual Status oplogDiskLocRegister( OperationContext* txn,
-                                             const OpTime& opTime );
+                                             const Timestamp& opTime );
 
         virtual void updateStatsAfterRepair(OperationContext* txn,
                                             long long numRecords,
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store_test.cpp
index b944e38329d..d8f8d6cc016 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store_test.cpp
@@ -515,7 +515,7 @@ namespace {
 
     StatusWith<RecordId> insertBSON(scoped_ptr<OperationContext>& opCtx,
                                    scoped_ptr<RecordStore>& rs,
-                                   const OpTime& opTime) {
+                                   const Timestamp& opTime) {
         BSONObj obj = BSON( "ts" << opTime );
         WriteUnitOfWork wuow(opCtx.get());
         WiredTigerRecordStore* wrs = checked_cast<WiredTigerRecordStore*>(rs.get());
@@ -540,33 +540,33 @@ namespace {
             scoped_ptr<OperationContext> opCtx(harnessHelper.newOperationContext());
 
             // always illegal
-            ASSERT_EQ(insertBSON(opCtx, rs, OpTime(2,-1)).getStatus(),
+            ASSERT_EQ(insertBSON(opCtx, rs, Timestamp(2,-1)).getStatus(),
                   ErrorCodes::BadValue);
 
             {
-                BSONObj obj = BSON("not_ts" << OpTime(2,1));
+                BSONObj obj = BSON("not_ts" << Timestamp(2,1));
                 ASSERT_EQ(rs->insertRecord(opCtx.get(), obj.objdata(), obj.objsize(),
                                            false ).getStatus(),
                           ErrorCodes::BadValue);
 
-                obj = BSON( "ts" << "not an OpTime" );
+                obj = BSON( "ts" << "not a Timestamp" );
                 ASSERT_EQ(rs->insertRecord(opCtx.get(), obj.objdata(), obj.objsize(),
                                            false ).getStatus(),
                           ErrorCodes::BadValue);
             }
 
             // currently dasserts
-            // ASSERT_EQ(insertBSON(opCtx, rs, BSON("ts" << OpTime(-2,1))).getStatus(),
+            // ASSERT_EQ(insertBSON(opCtx, rs, BSON("ts" << Timestamp(-2,1))).getStatus(),
             // ErrorCodes::BadValue);
 
             // success cases
-            ASSERT_EQ(insertBSON(opCtx, rs, OpTime(1,1)).getValue(),
+            ASSERT_EQ(insertBSON(opCtx, rs, Timestamp(1,1)).getValue(),
                       RecordId(1,1));
 
-            ASSERT_EQ(insertBSON(opCtx, rs, OpTime(1,2)).getValue(),
+            ASSERT_EQ(insertBSON(opCtx, rs, Timestamp(1,2)).getValue(),
                       RecordId(1,2));
 
-            ASSERT_EQ(insertBSON(opCtx, rs, OpTime(2,2)).getValue(),
+            ASSERT_EQ(insertBSON(opCtx, rs, Timestamp(2,2)).getValue(),
                       RecordId(2,2));
         }
 
@@ -628,7 +628,7 @@ namespace {
 
         scoped_ptr<OperationContext> opCtx(harnessHelper.newOperationContext());
 
-        BSONObj obj = BSON( "ts" << OpTime(2,-1) );
+        BSONObj obj = BSON( "ts" << Timestamp(2,-1) );
         {
             WriteUnitOfWork wuow( opCtx.get() );
             ASSERT_OK(rs->insertRecord(opCtx.get(), obj.objdata(),
@@ -746,7 +746,7 @@ namespace {
     RecordId _oplogOrderInsertOplog( OperationContext* txn,
                                     scoped_ptr<RecordStore>& rs,
                                     int inc ) {
-        OpTime opTime = OpTime(5,inc);
+        Timestamp opTime = Timestamp(5,inc);
         WiredTigerRecordStore* wrs = checked_cast<WiredTigerRecordStore*>(rs.get());
         Status status = wrs->oplogDiskLocRegister( txn, opTime );
         ASSERT_OK( status );
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
index 12c3380e760..7673bcddbac 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
@@ -31,6 +31,8 @@
 
 #define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kStorage
 
+#include <boost/thread.hpp>
+
 #include "mongo/db/storage/wiredtiger/wiredtiger_session_cache.h"
 
 #include "mongo/db/storage/wiredtiger/wiredtiger_kv_engine.h"
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_size_storer.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_size_storer.cpp
index 8d61fb17712..5d0affb7305 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_size_storer.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_size_storer.cpp
@@ -31,6 +31,7 @@
 
 #define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kStorage
 
+#include <boost/thread.hpp>
 #include <wiredtiger.h>
 
 #include "mongo/bson/bsonobj.h"
diff --git a/src/mongo/db/write_concern.cpp b/src/mongo/db/write_concern.cpp
index 8b1b7334813..a16352b34fc 100644
--- a/src/mongo/db/write_concern.cpp
+++ b/src/mongo/db/write_concern.cpp
@@ -191,7 +191,7 @@ namespace mongo {
     }
 
     Status waitForWriteConcern( OperationContext* txn,
-                                const OpTime& replOpTime,
+                                const Timestamp& replOpTime,
                                 WriteConcernResult* result ) {
 
         const WriteConcernOptions& writeConcern = txn->getWriteConcern();
diff --git a/src/mongo/db/write_concern.h b/src/mongo/db/write_concern.h
index c287d1ff8fd..0f375c9c069 100644
--- a/src/mongo/db/write_concern.h
+++ b/src/mongo/db/write_concern.h
@@ -94,7 +94,7 @@ namespace mongo {
      * Returns UnknownReplWriteConcern if the wMode specified was not enforceable
      */
     Status waitForWriteConcern( OperationContext* txn,
-                                const OpTime& replOpTime,
+                                const Timestamp& replOpTime,
                                 WriteConcernResult* result );
 
 
diff --git a/src/mongo/db/write_concern_options.cpp b/src/mongo/db/write_concern_options.cpp
index 5c0102ebc4a..50bf9cad040 100644
--- a/src/mongo/db/write_concern_options.cpp
+++ b/src/mongo/db/write_concern_options.cpp
@@ -27,9 +27,9 @@
 
 #include "mongo/db/write_concern_options.h"
 
-#include "mongo/bson/bson_field.h"
 #include "mongo/client/dbclientinterface.h"
 #include "mongo/db/field_parser.h"
+#include "mongo/db/jsobj.h"
 
 namespace mongo {