SERVER-13874 Make mongo::Milliseconds et al. aliases for equivalent stdx::chrono types.

Also introduces operators for adding stdx::chrono::duration to Date_t,
subtracting two Date_ts to get Milliseconds, and remove the use of
reinterpret_cast from the implementation of BSON Timestamp type.

106 files changed, 747 insertions, 596 deletions

diff --git a/src/mongo/bson/bsonelement.cpp b/src/mongo/bson/bsonelement.cpp
index 49f45c44a12..86efd0f7e27 100644
--- a/src/mongo/bson/bsonelement.cpp
+++ b/src/mongo/bson/bsonelement.cpp
@@ -201,7 +201,7 @@ namespace mongo {
                     s << "\"" << dateToISOStringLocal(date()) << "\"";
                 }
                 else {
-                    s << "{ \"$numberLong\" : \"" << static_cast<long long>(d.millis) << "\" }";
+                    s << "{ \"$numberLong\" : \"" << d.toMillisSinceEpoch() << "\" }";
                 }
                 s << " }";
             }
@@ -221,7 +221,7 @@ namespace mongo {
                     else {
                         // FIXME: This is not parseable by the shell, since it may not fit in a
                         // float
-                        s << d.millis;
+                        s << d.toMillisSinceEpoch();
                     }
                 }
                 else {
@@ -266,10 +266,14 @@ namespace mongo {
 
         case bsonTimestamp:
             if ( format == TenGen ) {
-                s << "Timestamp( " << ( timestampTime() / 1000 ) << ", " << timestampInc() << " )";
+                s << "Timestamp( "
+                  << durationCount<Seconds>(timestampTime().toDurationSinceEpoch())
+                  << ", " << timestampInc() << " )";
             }
             else {
-                s << "{ \"$timestamp\" : { \"t\" : " << ( timestampTime() / 1000 ) << ", \"i\" : " << timestampInc() << " } }";
+                s << "{ \"$timestamp\" : { \"t\" : "
+                  << durationCount<Seconds>(timestampTime().toDurationSinceEpoch())
+                  << ", \"i\" : " << timestampInc() << " } }";
             }
             break;
 
@@ -616,7 +620,7 @@ namespace mongo {
             s << "EOO";
             break;
         case mongo::Date:
-            s << "new Date(" << (long long) date() << ')';
+            s << "new Date(" << date().toMillisSinceEpoch() << ')';
             break;
         case RegEx: {
             s << "/" << regex() << '/';
@@ -701,7 +705,7 @@ namespace mongo {
             }
             break;
         case bsonTimestamp:
-            s << "Timestamp " << timestampTime() << "|" << timestampInc();
+            s << "Timestamp " << timestampTime().toMillisSinceEpoch() << "|" << timestampInc();
             break;
         default:
             s << "?type=" << type();
@@ -852,8 +856,8 @@ namespace mongo {
         case Date:
             // Signed comparisons for Dates.
             {
-                long long a = (long long) l.Date().millis;
-                long long b = (long long) r.Date().millis;
+                const Date_t a = l.Date();
+                const Date_t b = r.Date();
                 if( a < b ) 
                     return -1;
                 return a == b ? 0 : 1;
diff --git a/src/mongo/bson/bsonelement.h b/src/mongo/bson/bsonelement.h
index c4fd19c77b4..25d9e895b49 100644
--- a/src/mongo/bson/bsonelement.h
+++ b/src/mongo/bson/bsonelement.h
@@ -211,7 +211,8 @@ namespace mongo {
             @see Bool(), trueValue()
         */
         Date_t date() const {
-            return Date_t(ConstDataView(value()).read<LittleEndian<unsigned long long>>());
+            return Date_t::fromMillisSinceEpoch(
+                    ConstDataView(value()).read<LittleEndian<long long>>());
         }
 
         /** Convert the value to boolean, regardless of its type, in a javascript-like fashion
@@ -464,7 +465,7 @@ namespace mongo {
 
         Date_t timestampTime() const {
             unsigned long long t = ConstDataView(value() + 4).read<LittleEndian<unsigned int>>();
-            return t * 1000;
+            return Date_t::fromMillisSinceEpoch(t * 1000);
         }
         unsigned int timestampInc() const {
             return ConstDataView(value()).read<LittleEndian<unsigned int>>();
diff --git a/src/mongo/bson/bsonobjbuilder.cpp b/src/mongo/bson/bsonobjbuilder.cpp
index d0fd2665ff3..a9878b28adc 100644
--- a/src/mongo/bson/bsonobjbuilder.cpp
+++ b/src/mongo/bson/bsonobjbuilder.cpp
@@ -109,7 +109,9 @@ namespace mongo {
         case String:
             appendMinForType( fieldName, Object ); return;
         case Date:
-            appendDate( fieldName , std::numeric_limits<long long>::max() ); return;
+            appendDate(fieldName,
+                       Date_t::fromMillisSinceEpoch(std::numeric_limits<long long>::max()));
+            return;
         case bsonTimestamp:
             append( fieldName , Timestamp::max() ); return;
         case Undefined: // shared with EOO
@@ -196,16 +198,9 @@ namespace mongo {
     }
 
     BSONObjBuilder& BSONObjBuilder::appendDate(StringData fieldName, Date_t dt) {
-        /* easy to pass a time_t to this and get a bad result.  thus this warning. */
-        if ( kDebugBuild && dt > 0 && dt <= 0xffffffff ) {
-            static int n;
-            if( n++ == 0 )
-                log() << "DEV WARNING appendDate() called with a tiny (but nonzero) date" << std::endl;
-        }
-
         _b.appendNum((char) Date);
         _b.appendStr(fieldName);
-        _b.appendNum(dt);
+        _b.appendNum(dt.toMillisSinceEpoch());
         return *this;
     }
 
diff --git a/src/mongo/bson/json.cpp b/src/mongo/bson/json.cpp
index 2b13e318e44..3bf5c531cd0 100644
--- a/src/mongo/bson/json.cpp
+++ b/src/mongo/bson/json.cpp
@@ -471,12 +471,12 @@ namespace mongo {
             if (!ret.isOK()) {
                 return ret;
             }
-            date = numberLong;
+            date = Date_t::fromMillisSinceEpoch(numberLong);
         }
         else {
             // SERVER-11920: We should use parseNumberFromString here, but that function requires
             // that we know ahead of time where the number ends, which is not currently the case.
-            date = static_cast<unsigned long long>(strtoll(_input, &endptr, 10));
+            date = Date_t::fromMillisSinceEpoch(strtoll(_input, &endptr, 10));
             if (_input == endptr) {
                 return parseError("Date expecting integer milliseconds");
             }
@@ -487,7 +487,8 @@ namespace mongo {
                 // SERVER-11920: We should use parseNumberFromString here, but that function
                 // requires that we know ahead of time where the number ends, which is not currently
                 // the case.
-                date = strtoull(_input, &endptr, 10);
+                date = Date_t::fromMillisSinceEpoch(
+                        static_cast<long long>(strtoull(_input, &endptr, 10)));
                 if (errno == ERANGE) {
                     return parseError("Date milliseconds overflow");
                 }
@@ -753,7 +754,7 @@ namespace mongo {
         char* endptr;
         // SERVER-11920: We should use parseNumberFromString here, but that function requires that
         // we know ahead of time where the number ends, which is not currently the case.
-        Date_t date = static_cast<unsigned long long>(strtoll(_input, &endptr, 10));
+        Date_t date = Date_t::fromMillisSinceEpoch(strtoll(_input, &endptr, 10));
         if (_input == endptr) {
             return parseError("Date expecting integer milliseconds");
         }
@@ -763,7 +764,8 @@ namespace mongo {
             errno = 0;
             // SERVER-11920: We should use parseNumberFromString here, but that function requires
             // that we know ahead of time where the number ends, which is not currently the case.
-            date = strtoull(_input, &endptr, 10);
+            date = Date_t::fromMillisSinceEpoch(
+                    static_cast<long long>(strtoull(_input, &endptr, 10)));
             if (errno == ERANGE) {
                 return parseError("Date milliseconds overflow");
             }
diff --git a/src/mongo/bson/oid.cpp b/src/mongo/bson/oid.cpp
index 853299d5bfe..e9c6b87eb3a 100644
--- a/src/mongo/bson/oid.cpp
+++ b/src/mongo/bson/oid.cpp
@@ -151,7 +151,7 @@ namespace {
     }
 
     void OID::init(Date_t date, bool max) {
-        setTimestamp(uint32_t(date / 1000));
+        setTimestamp(uint32_t(date.toMillisSinceEpoch() / 1000));
         uint64_t rest = max ? std::numeric_limits<uint64_t>::max() : 0u;
         std::memcpy(_view().view(kInstanceUniqueOffset), &rest,
                     kInstanceUniqueSize + kIncrementSize);
diff --git a/src/mongo/bson/oid.h b/src/mongo/bson/oid.h
index df29065bb5e..a4ae3269d5f 100644
--- a/src/mongo/bson/oid.h
+++ b/src/mongo/bson/oid.h
@@ -140,7 +140,7 @@ namespace mongo {
         void init( Date_t date, bool max=false );
 
         time_t asTimeT() const;
-        Date_t asDateT() const { return asTimeT() * 1000LL; }
+        Date_t asDateT() const { return Date_t::fromMillisSinceEpoch(asTimeT() * 1000LL); }
 
         // True iff the OID is not empty
         bool isSet() const {
diff --git a/src/mongo/bson/timestamp.h b/src/mongo/bson/timestamp.h
index b223b5deb50..8565cc80847 100644
--- a/src/mongo/bson/timestamp.h
+++ b/src/mongo/bson/timestamp.h
@@ -30,51 +30,56 @@
 #include "mongo/base/data_view.h"
 #include "mongo/bson/util/builder.h"
 #include "mongo/util/assert_util.h"
+#include "mongo/util/time_support.h"
 
 namespace mongo {
 
-    /* Timestamp: A combination of current second plus an ordinal value.
+    /**
+     * Timestamp: A combination of a count of seconds since the POSIX epoch plus an ordinal value.
      */
-#pragma pack(4)
     class Timestamp {
-        unsigned i; // ordinal comes first so we can do a single 64 bit compare on little endian
-        unsigned secs;
     public:
+        // Maximum Timestamp value.
+        static Timestamp max();
+
+        /**
+         * DEPRECATED Constructor that builds a Timestamp from a Date_t by using the
+         * high-order 4 bytes of "date" for the "secs" field and the low-order 4 bytes
+         * for the "i" field.
+         */
+        explicit Timestamp(Date_t date) : Timestamp(date.toULL()) {}
+
+        /**
+         * DEPRECATED Constructor that builds a Timestamp from a 64-bit unsigned integer by using
+         * the high-order 4 bytes of "v" for the "secs" field and the low-order 4 bytes for the "i"
+         * field."
+         */
+        explicit Timestamp(unsigned long long v) : Timestamp(v >> 32, v) {}
+
+        Timestamp(Seconds s, unsigned increment) : Timestamp(s.count(), increment) {}
+
+        Timestamp(unsigned a, unsigned b) : i(b), secs(a) {
+            dassert(secs <= std::numeric_limits<int>::max());
+        }
+
+        Timestamp() : i(0), secs(0) {}
+
         unsigned getSecs() const {
             return secs;
         }
+
         unsigned getInc() const {
             return i;
         }
 
-        Timestamp(Date_t date) {
-            reinterpret_cast<unsigned long long&>(*this) = date.millis;
-            dassert( (int)secs >= 0 );
-        }
-
-        Timestamp(unsigned a, unsigned b) {
-            secs = a;
-            i = b;
-            dassert( (int)secs >= 0 );
-        }
-        Timestamp( const Timestamp& other ) { 
-            secs = other.secs;
-            i = other.i;
-            dassert( (int)secs >= 0 );
-        }
-        Timestamp() {
-            secs = 0;
-            i = 0;
-        }
-
-        // Maximum Timestamp value.
-        static Timestamp max();
-
         unsigned long long asULL() const {
-            return reinterpret_cast<const unsigned long long*>(&i)[0];
+            unsigned long long result = secs;
+            result <<= 32;
+            result |= i;
+            return result;
         }
         long long asLL() const {
-            return reinterpret_cast<const long long*>(&i)[0];
+            return static_cast<long long>(asULL());
         }
 
         bool isNull() const { return secs == 0; }
@@ -86,31 +91,33 @@ namespace mongo {
         std::string toString() const;
 
         bool operator==(const Timestamp& r) const {
-            return i == r.i && secs == r.secs;
+            return tie() == r.tie();
         }
         bool operator!=(const Timestamp& r) const {
-            return !(*this == r);
+            return tie() != r.tie();
         }
         bool operator<(const Timestamp& r) const {
-            if ( secs != r.secs )
-                return secs < r.secs;
-            return i < r.i;
+            return tie() < r.tie();
         }
         bool operator<=(const Timestamp& r) const {
-            return *this < r || *this == r;
+            return tie() <= r.tie();
         }
         bool operator>(const Timestamp& r) const {
-            return !(*this <= r);
+            return tie() > r.tie();
         }
         bool operator>=(const Timestamp& r) const {
-            return !(*this < r);
+            return tie() >= r.tie();
         }
 
         // Append the BSON representation of this Timestamp to the given BufBuilder with the given
         // name. This lives here because Timestamp manages its own serialization format.
         void append(BufBuilder& builder, const StringData& fieldName) const;
 
+    private:
+        std::tuple<unsigned, unsigned> tie() const { return std::tie(secs, i); }
+
+        unsigned i; // ordinal comes first so we can do a single 64 bit compare on little endian
+        unsigned secs;
     };
-#pragma pack()
 
 } // namespace mongo
diff --git a/src/mongo/client/connection_pool.cpp b/src/mongo/client/connection_pool.cpp
index dda86a0675c..ed994b25c33 100644
--- a/src/mongo/client/connection_pool.cpp
+++ b/src/mongo/client/connection_pool.cpp
@@ -39,22 +39,17 @@
 namespace mongo {
 namespace {
 
-    const unsigned long long kNeverTooStale = std::numeric_limits<unsigned long long>::max();
+    const Date_t kNeverTooStale = Date_t::max();
 
-    // 5 Minutes (Note: Must be larger than kMaxConnectionAge below)
-    const long long kCleanUpInterval = 5 * 60 * 1000;
+    const Minutes kCleanUpInterval(5); // Note: Must be larger than kMaxConnectionAge below)
     const Seconds kMaxConnectionAge(30);
 
 } // namespace
 
-    ConnectionPool::ConnectionPool(int messagingPortTags)
-        : _messagingPortTags(messagingPortTags),
-          _lastCleanUpTime(0ULL) {
-
-    }
+    ConnectionPool::ConnectionPool(int messagingPortTags) : _messagingPortTags(messagingPortTags) {}
 
     ConnectionPool::~ConnectionPool() {
-        cleanUpOlderThan(Date_t(~0ULL));
+        cleanUpOlderThan(Date_t::max());
 
         invariant(_connections.empty());
         invariant(_inUseConnections.empty());
@@ -91,8 +86,7 @@ namespace {
     }
 
     bool ConnectionPool::_shouldKeepConnection(Date_t now, const ConnectionInfo& connInfo) const {
-        const Date_t expirationDate =
-                connInfo.creationDate + kMaxConnectionAge.total_milliseconds();
+        const Date_t expirationDate = connInfo.creationDate + kMaxConnectionAge;
         if (expirationDate <= now) {
             return false;
         }
@@ -120,7 +114,7 @@ namespace {
                     ConnectionList connList = _connections.find(itr->first)->second;
                     _cleanUpOlderThan_inlock(now, &connList);
                     invariant(connList.empty());
-                    itr->second = Date_t(kNeverTooStale);
+                    itr->second = kNeverTooStale;
                 }
             }
 
@@ -144,7 +138,7 @@ namespace {
             _cleanUpOlderThan_inlock(now, &hostConns->second);
             if (hostConns->second.empty()) {
                 // prevent host from causing unnecessary cleanups
-                _lastUsedHosts[hostConns->first] = Date_t(kNeverTooStale);
+                _lastUsedHosts[hostConns->first] = kNeverTooStale;
                 break;
             }
 
@@ -157,9 +151,9 @@ namespace {
             try {
                 if (candidate->conn->isStillConnected()) {
                     // setSoTimeout takes a double representing the number of seconds for send and
-                    // receive timeouts.  Thus, we must take total_milliseconds() and divide by
+                    // receive timeouts.  Thus, we must take count() and divide by
                     // 1000.0 to get the number of seconds with a fractional part.
-                    candidate->conn->setSoTimeout(timeout.total_milliseconds() / 1000.0);
+                    candidate->conn->setSoTimeout(timeout.count() / 1000.0);
                     return candidate;
                 }
             }
@@ -178,9 +172,9 @@ namespace {
         std::auto_ptr<DBClientConnection> conn(new DBClientConnection);
 
         // setSoTimeout takes a double representing the number of seconds for send and receive
-        // timeouts.  Thus, we must take total_milliseconds() and divide by 1000.0 to get the number
+        // timeouts.  Thus, we must take count() and divide by 1000.0 to get the number
         // of seconds with a fractional part.
-        conn->setSoTimeout(timeout.total_milliseconds() / 1000.0);
+        conn->setSoTimeout(timeout.count() / 1000.0);
         std::string errmsg;
         uassert(28640,
                 str::stream() << "Failed attempt to connect to "
diff --git a/src/mongo/client/connection_pool.h b/src/mongo/client/connection_pool.h
index 2d31affcc00..daf36d87337 100644
--- a/src/mongo/client/connection_pool.h
+++ b/src/mongo/client/connection_pool.h
@@ -52,7 +52,7 @@ namespace mongo {
          * Information about a connection in the pool.
          */
         struct ConnectionInfo {
-            ConnectionInfo() : conn(NULL), creationDate(0ULL) {}
+            ConnectionInfo() : conn(NULL) {}
             ConnectionInfo(DBClientConnection* theConn, Date_t date)
                 : conn(theConn),
                   creationDate(date) {}
diff --git a/src/mongo/client/remote_command_executor.cpp b/src/mongo/client/remote_command_executor.cpp
index 23688c55827..546bfd54c02 100644
--- a/src/mongo/client/remote_command_executor.cpp
+++ b/src/mongo/client/remote_command_executor.cpp
@@ -34,6 +34,9 @@
 
 namespace mongo {
 
+    const Milliseconds kNoTimeout{-1};
+    const Date_t kNoExpirationDate{Date_t::max()};
+
     std::string RemoteCommandRequest::toString() const {
         str::stream out;
         out << "RemoteCommand -- target:" << target.toString() << " db:" << dbname;
diff --git a/src/mongo/client/remote_command_executor.h b/src/mongo/client/remote_command_executor.h
index 9eb7f5cf57c..294c41b3cac 100644
--- a/src/mongo/client/remote_command_executor.h
+++ b/src/mongo/client/remote_command_executor.h
@@ -40,8 +40,8 @@ namespace mongo {
     template<typename T> class StatusWith;
 
 
-    const Milliseconds kNoTimeout(-1);
-    const Date_t kNoExpirationDate(-1);
+    extern const Milliseconds kNoTimeout;
+    extern const Date_t kNoExpirationDate;
 
 
     /**
diff --git a/src/mongo/client/remote_command_executor_impl.cpp b/src/mongo/client/remote_command_executor_impl.cpp
index 3bac4886a5e..79bb58ce88e 100644
--- a/src/mongo/client/remote_command_executor_impl.cpp
+++ b/src/mongo/client/remote_command_executor_impl.cpp
@@ -42,29 +42,22 @@ namespace mongo {
 namespace {
 
     /**
-     * Calculates the timeout for a network operation expiring at "expDate", given that it is now
-     * "nowDate".
+     * Calculates the timeout for a network operation expiring at "expDate", given
+     * that it is now "nowDate".
      *
-     * Returns 0 to indicate no expiration date, a number of milliseconds until "expDate", or
+     * Returns 0ms to indicate no expiration date, a number of milliseconds until "expDate", or
      * ErrorCodes::ExceededTimeLimit if "expDate" is not later than "nowDate".
-     *
-     * TODO: Change return type to StatusWith<Milliseconds> once Milliseconds supports default
-     * construction or StatusWith<T> supports not constructing T when the result is a non-OK
-     * status.
      */
-    StatusWith<int64_t> getTimeoutMillis(const Date_t expDate, const Date_t nowDate) {
+    StatusWith<Milliseconds> getTimeoutMillis(const Date_t expDate, const Date_t nowDate) {
         if (expDate == kNoExpirationDate) {
-            return StatusWith<int64_t>(0);
+            return Milliseconds(0);
         }
-
         if (expDate <= nowDate) {
-            return StatusWith<int64_t>(
-                        ErrorCodes::ExceededTimeLimit,
-                        str::stream() << "Went to run command, but it was too late. "
-                                         "Expiration was set to " << dateToISOStringUTC(expDate));
+            return {ErrorCodes::ExceededTimeLimit,
+                    str::stream() << "Went to run command, but it was too late. "
+                    "Expiration was set to " << dateToISOStringUTC(expDate)};
         }
-
-        return StatusWith<int64_t>(expDate.asInt64() - nowDate.asInt64());
+        return expDate - nowDate;
     }
 
     /**
@@ -220,9 +213,8 @@ namespace {
         try {
             BSONObj output;
 
-            const Date_t requestStartDate = curTimeMillis64();
-            StatusWith<int64_t> timeoutMillis = getTimeoutMillis(request.expirationDate,
-                                                                 requestStartDate);
+            const Date_t requestStartDate = Date_t::now();
+            const auto timeoutMillis = getTimeoutMillis(request.expirationDate, requestStartDate);
             if (!timeoutMillis.isOK()) {
                 return StatusWith<RemoteCommandResponse>(timeoutMillis.getStatus());
             }
@@ -230,7 +222,7 @@ namespace {
             ConnectionPool::ConnectionPtr conn(&_connPool,
                                                request.target,
                                                requestStartDate,
-                                               Milliseconds(timeoutMillis.getValue()));
+                                               timeoutMillis.getValue());
 
             bool ok = conn.get()->runCommand(request.dbname, request.cmdObj, output);
 
@@ -260,7 +252,7 @@ namespace {
                 }
             }
 
-            const Date_t requestFinishDate = curTimeMillis64();
+            const Date_t requestFinishDate = Date_t::now();
             conn.done(requestFinishDate);
 
             return StatusWith<RemoteCommandResponse>(
diff --git a/src/mongo/db/auth/user_cache_invalidator_job.cpp b/src/mongo/db/auth/user_cache_invalidator_job.cpp
index 7669d0201bc..f6a17cba04a 100644
--- a/src/mongo/db/auth/user_cache_invalidator_job.cpp
+++ b/src/mongo/db/auth/user_cache_invalidator_job.cpp
@@ -138,14 +138,11 @@ namespace {
 
         while (true) {
             boost::unique_lock<boost::mutex> lock(invalidationIntervalMutex);
-            Date_t sleepUntil = Date_t(
-                    lastInvalidationTime.millis + userCacheInvalidationIntervalSecs * 1000);
+            Date_t sleepUntil = lastInvalidationTime + Seconds(userCacheInvalidationIntervalSecs);
             Date_t now(curTimeMillis64());
-            while (now.millis < sleepUntil.millis) {
-                invalidationIntervalChangedCondition.timed_wait(lock,
-                                                                Milliseconds(sleepUntil - now));
-                sleepUntil = Date_t(
-                        lastInvalidationTime.millis + (userCacheInvalidationIntervalSecs * 1000));
+            while (now < sleepUntil) {
+                invalidationIntervalChangedCondition.wait_for(lock, sleepUntil - now);
+                sleepUntil = lastInvalidationTime + Seconds(userCacheInvalidationIntervalSecs);
                 now = Date_t(curTimeMillis64());
             }
             lastInvalidationTime = now;
diff --git a/src/mongo/db/concurrency/lock_state.cpp b/src/mongo/db/concurrency/lock_state.cpp
index d5d5654fbc5..b2047138669 100644
--- a/src/mongo/db/concurrency/lock_state.cpp
+++ b/src/mongo/db/concurrency/lock_state.cpp
@@ -229,7 +229,7 @@ namespace {
     LockResult CondVarLockGrantNotification::wait(unsigned timeoutMs) {
         boost::unique_lock<boost::mutex> lock(_mutex);
         while (_result == LOCK_INVALID) {
-            if (!_cond.timed_wait(lock, Milliseconds(timeoutMs))) {
+            if (boost::cv_status::timeout == _cond.wait_for(lock, Milliseconds(timeoutMs))) {
                 // Timeout
                 return LOCK_TIMEOUT;
             }
diff --git a/src/mongo/db/db.cpp b/src/mongo/db/db.cpp
index 1b4963fa4b0..fa360169fa0 100644
--- a/src/mongo/db/db.cpp
+++ b/src/mongo/db/db.cpp
@@ -205,7 +205,7 @@ namespace mongo {
         toLog.append( "hostname", getHostNameCached() );
 
         toLog.appendTimeT( "startTime", time(0) );
-        toLog.append( "startTimeLocal", dateToCtimeString(curTimeMillis64()) );
+        toLog.append( "startTimeLocal", dateToCtimeString(Date_t::now()) );
 
         toLog.append("cmdLine", serverGlobalParams.parsedOpts);
         toLog.append( "pid", ProcessId::getCurrent().asLongLong() );
diff --git a/src/mongo/db/dbcommands.cpp b/src/mongo/db/dbcommands.cpp
index 89159347ed0..c59661c2e4d 100644
--- a/src/mongo/db/dbcommands.cpp
+++ b/src/mongo/db/dbcommands.cpp
@@ -136,8 +136,8 @@ namespace mongo {
             Status status = repl::getGlobalReplicationCoordinator()->stepDown(
                                     txn,
                                     force,
-                                    repl::ReplicationCoordinator::Milliseconds(timeoutSecs * 1000),
-                                    repl::ReplicationCoordinator::Milliseconds(120 * 1000));
+                                    Seconds(timeoutSecs),
+                                    Seconds(120));
             if (!status.isOK() && status.code() != ErrorCodes::NotMaster) { // ignore not master
                 return appendCommandStatus(result, status);
             }
diff --git a/src/mongo/db/dbhelpers.cpp b/src/mongo/db/dbhelpers.cpp
index 1d7cae4632c..24be8b1f4f3 100644
--- a/src/mongo/db/dbhelpers.cpp
+++ b/src/mongo/db/dbhelpers.cpp
@@ -355,7 +355,7 @@ namespace mongo {
 
         long long numDeleted = 0;
         
-        long long millisWaitingForReplication = 0;
+        Milliseconds millisWaitingForReplication{0};
 
         while ( 1 ) {
             // Scoping for write lock.
@@ -468,14 +468,14 @@ namespace mongo {
                 else {
                     massertStatusOK(replStatus.status);
                 }
-                millisWaitingForReplication += replStatus.duration.total_milliseconds();
+                millisWaitingForReplication += replStatus.duration;
             }
         }
         
         if (writeConcern.shouldWaitForOtherNodes())
             log(LogComponent::kSharding)
                   << "Helpers::removeRangeUnlocked time spent waiting for replication: "
-                  << millisWaitingForReplication << "ms" << endl;
+                  << durationCount<Milliseconds>(millisWaitingForReplication) << "ms" << endl;
         
         MONGO_LOG_COMPONENT(1, LogComponent::kSharding)
                << "end removal of " << min << " to " << max << " in " << ns
diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index defc38d8c12..e8c121c2b04 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -422,7 +422,7 @@ namespace {
         if (haveDate) {
             if (totalType == NumberDouble)
                 longTotal = static_cast<long long>(doubleTotal);
-            return Value(Date_t(longTotal));
+            return Value(Date_t::fromMillisSinceEpoch(longTotal));
         }
         else if (totalType == NumberLong) {
             return Value(longTotal);
@@ -2548,7 +2548,7 @@ namespace {
             }
             else if (rhs.numeric()) {
                 long long millisSinceEpoch = lhs.getDate() - rhs.coerceToLong();
-                return Value(Date_t(millisSinceEpoch));
+                return Value(Date_t::fromMillisSinceEpoch(millisSinceEpoch));
             }
             else {
                 uasserted(16613, str::stream() << "cant $subtract a "
diff --git a/src/mongo/db/pipeline/value.cpp b/src/mongo/db/pipeline/value.cpp
index b156d290613..c949601ac4d 100644
--- a/src/mongo/db/pipeline/value.cpp
+++ b/src/mongo/db/pipeline/value.cpp
@@ -186,8 +186,7 @@ namespace mongo {
             break;
 
         case Date:
-            // this is really signed but typed as unsigned for historical reasons
-            _storage.dateValue = static_cast<long long>(elem.date().millis);
+            _storage.dateValue = elem.date().toMillisSinceEpoch();
             break;
 
         case RegEx: {
@@ -288,7 +287,7 @@ namespace mongo {
         case NumberDouble: return builder << val.getDouble();
         case String:       return builder << val.getStringData();
         case Bool:         return builder << val.getBool();
-        case Date:         return builder << Date_t(val.getDate());
+        case Date:         return builder << Date_t::fromMillisSinceEpoch(val.getDate());
         case bsonTimestamp:    return builder << val.getTimestamp();
         case Object:       return builder << val.getDocument();
         case Symbol:       return builder << BSONSymbol(val.getStringData());
@@ -1018,7 +1017,7 @@ namespace mongo {
         case NumberLong:   return Value(buf.read<long long>());
         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 Date:         return Value(Date_t::fromMillisSinceEpoch(buf.read<long long>()));
         case bsonTimestamp:  return Value(buf.read<Timestamp>());
 
         // types that are like strings
diff --git a/src/mongo/db/pipeline/value.h b/src/mongo/db/pipeline/value.h
index 5324cc1b432..ecc66719d11 100644
--- a/src/mongo/db/pipeline/value.h
+++ b/src/mongo/db/pipeline/value.h
@@ -91,9 +91,7 @@ namespace mongo {
         explicit Value(const UndefinedLabeler&)   : _storage(Undefined) {} // BSONUndefined
         explicit Value(const MinKeyLabeler&)      : _storage(MinKey) {}    // MINKEY
         explicit Value(const MaxKeyLabeler&)      : _storage(MaxKey) {}    // MAXKEY
-        explicit Value(const Date_t& date)
-            : _storage(Date, static_cast<long long>(date.millis)) // millis really signed
-        {}
+        explicit Value(const Date_t& date) : _storage(Date, date.toMillisSinceEpoch()) {}
 
         // TODO: add an unsafe version that can share storage with the BSONElement
         /// Deep-convert from BSONElement to Value
@@ -317,7 +315,7 @@ namespace mongo {
 
     inline Timestamp Value::getTimestamp() const {
         verify(getType() == bsonTimestamp);
-        return Date_t(_storage.timestampValue);
+        return Timestamp(_storage.timestampValue);
     }
 
     inline const char* Value::getRegex() const {
diff --git a/src/mongo/db/range_deleter.cpp b/src/mongo/db/range_deleter.cpp
index bde2e3ad36c..caa2c63804c 100644
--- a/src/mongo/db/range_deleter.cpp
+++ b/src/mongo/db/range_deleter.cpp
@@ -83,28 +83,28 @@ namespace mongo {
         // We always log the first cursors waiting message (so we have cursor ids in the logs).
         // After 15 minutes (the cursor timeout period), we start logging additional messages at
         // a 1 minute interval.
-        static const long long kLogCursorsThresholdMillis = 15 * 60 * 1000;
-        static const long long kLogCursorsIntervalMillis = 1 * 60 * 1000;
+        static const auto kLogCursorsThreshold = stdx::chrono::minutes{15};
+        static const auto kLogCursorsInterval = stdx::chrono::minutes{1};
 
         Date_t currentTime = jsTime();
-        long long elapsedMillisSinceQueued = 0;
+        Milliseconds elapsedMillisSinceQueued{0};
 
         // We always log the first message when lastLoggedTime == 0
-        if (entry->lastLoggedTS != 0) {
+        if (entry->lastLoggedTS != Date_t()) {
 
             if (currentTime > entry->stats.queueStartTS)
                 elapsedMillisSinceQueued = currentTime - entry->stats.queueStartTS;
 
             // Not logging, threshold not passed
-            if (elapsedMillisSinceQueued < kLogCursorsThresholdMillis)
+            if (elapsedMillisSinceQueued < kLogCursorsThreshold)
                 return;
 
-            long long elapsedMillisSinceLog = 0;
+            Milliseconds elapsedMillisSinceLog{0};
             if (currentTime > entry->lastLoggedTS)
                 elapsedMillisSinceLog = currentTime - entry->lastLoggedTS;
 
             // Not logging, logged a short time ago
-            if (elapsedMillisSinceLog < kLogCursorsIntervalMillis)
+            if (elapsedMillisSinceLog < kLogCursorsInterval)
                 return;
         }
 
@@ -119,9 +119,10 @@ namespace mongo {
         log() << "waiting for open cursors before removing range "
               << "[" << entry->options.range.minKey << ", " << entry->options.range.maxKey << ") "
               << "in " << entry->options.range.ns
-              << (entry->lastLoggedTS == 0 ?
+              << (entry->lastLoggedTS == Date_t() ?
                   string("") :
-                  string(str::stream() << ", elapsed secs: " << elapsedMillisSinceQueued / 1000))
+                  string(str::stream() << ", elapsed secs: " <<
+                         durationCount<Seconds>(elapsedMillisSinceQueued)))
               << ", cursor ids: [" << string(cursorList) << "]";
 
         entry->lastLoggedTS = currentTime;
@@ -276,21 +277,23 @@ namespace {
         repl::ReplicationCoordinator::StatusAndDuration replStatus =
                 repl::getGlobalReplicationCoordinator()->awaitReplicationOfLastOpForClient(
                         txn, writeConcern);
-        repl::ReplicationCoordinator::Milliseconds elapsedTime = replStatus.duration;
+        Milliseconds elapsedTime = replStatus.duration;
         if (replStatus.status.code() == ErrorCodes::ExceededTimeLimit) {
             *errMsg = str::stream() << "rangeDeleter timed out after "
-                                    << elapsedTime.total_seconds() << " seconds while waiting"
-                                    << " for deletions to be replicated to majority nodes";
+                                    << durationCount<Seconds>(elapsedTime)
+                                    << " seconds while waiting"
+                                       " for deletions to be replicated to majority nodes";
             log() << *errMsg;
         }
         else if (replStatus.status.code() == ErrorCodes::NotMaster) {
             *errMsg = str::stream() << "rangeDeleter no longer PRIMARY after "
-                                    << elapsedTime.total_seconds() << " seconds while waiting"
-                                    << " for deletions to be replicated to majority nodes";
+                                    << durationCount<Seconds>(elapsedTime)
+                                    << " seconds while waiting"
+                                       " for deletions to be replicated to majority nodes";
         }
         else {
-            LOG(elapsedTime.total_seconds() < 30 ? 1 : 0)
-                << "rangeDeleter took " << elapsedTime.total_seconds() << " seconds "
+            LOG(elapsedTime < Seconds(30) ? 1 : 0)
+                << "rangeDeleter took " << durationCount<Seconds>(elapsedTime) << " seconds "
                 << " waiting for deletes to be replicated to majority nodes";
 
             fassert(18512, replStatus.status);
@@ -601,10 +604,7 @@ namespace {
     }
 
     RangeDeleteEntry::RangeDeleteEntry(const RangeDeleterOptions& options)
-        : options(options),
-          notifyDone(NULL),
-          lastLoggedTS(0) {
-    }
+        : options(options), notifyDone(NULL) {}
 
     BSONObj RangeDeleteEntry::toBSON() const {
         BSONObjBuilder builder;
diff --git a/src/mongo/db/repl/base_cloner_test_fixture.cpp b/src/mongo/db/repl/base_cloner_test_fixture.cpp
index 45d1ca8b29d..2abe7d75a01 100644
--- a/src/mongo/db/repl/base_cloner_test_fixture.cpp
+++ b/src/mongo/db/repl/base_cloner_test_fixture.cpp
@@ -131,7 +131,7 @@ namespace repl {
         boost::unique_lock<boost::mutex> lk(_mutex);
         if (_status == getDefaultStatus()) {
             try {
-                _setStatusCondition.timed_wait(lk, ReplicationExecutor::Milliseconds(1000));
+                _setStatusCondition.wait_for(lk, Milliseconds(1000));
             }
             catch (const boost::thread_interrupted&) {
             }
@@ -142,7 +142,7 @@ namespace repl {
     void BaseClonerTest::scheduleNetworkResponse(NetworkOperationIterator noi,
                                                     const BSONObj& obj) {
         auto net = getNet();
-        ReplicationExecutor::Milliseconds millis(0);
+        Milliseconds millis(0);
         RemoteCommandResponse response(obj, millis);
         ReplicationExecutor::ResponseStatus responseStatus(response);
         net->scheduleResponse(noi, net->now(), responseStatus);
diff --git a/src/mongo/db/repl/check_quorum_for_config_change_test.cpp b/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
index 677141c727e..dbb5fb562f1 100644
--- a/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
+++ b/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
@@ -190,12 +190,12 @@ namespace {
         const int numCommandsExpected = config.getNumMembers() - 1;
         for (int i = 0; i < numCommandsExpected; ++i) {
             _net->scheduleResponse(_net->getNextReadyRequest(),
-                                   startDate + 10,
+                                   startDate + Milliseconds(10),
                                    ResponseStatus(ErrorCodes::NoSuchKey, "No reply"));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NodeNotFound, status);
         ASSERT_REASON_CONTAINS(
@@ -248,11 +248,11 @@ namespace {
             ASSERT(seenHosts.insert(request.target).second) <<
                 "Already saw " << request.target.toString();
             _net->scheduleResponse(noi,
-                                   startDate + 10,
+                                   startDate + Milliseconds(10),
                                    ResponseStatus(RemoteCommandResponse(
                                                           BSON("ok" << 1), Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         ASSERT_OK(waitForQuorumCheck());
     }
@@ -291,17 +291,17 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h2", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(ErrorCodes::NoSuchKey, "No response"));
             }
             else {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 1), Milliseconds(8))));
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NodeNotFound, status);
@@ -346,19 +346,19 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h4", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 0 << "mismatch" << true),
                                                               Milliseconds(8))));
             }
             else {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 1), Milliseconds(8))));
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NewReplicaSetConfigurationIncompatible, status);
@@ -402,7 +402,7 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h5", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 0 <<
                                                                    "set" << "rs0" <<
@@ -411,12 +411,12 @@ namespace {
             }
             else {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 1), Milliseconds(8))));
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NewReplicaSetConfigurationIncompatible, status);
@@ -463,7 +463,7 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h5", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 0 <<
                                                                    "set" << "rs0" <<
@@ -474,7 +474,7 @@ namespace {
                 _net->blackHole(noi);
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NewReplicaSetConfigurationIncompatible, status);
@@ -522,7 +522,7 @@ namespace {
             hbResp.noteHasData();
             if (request.target == HostAndPort("h5", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               hbResp.toBSON(),
                                                               Milliseconds(8))));
@@ -531,7 +531,7 @@ namespace {
                 _net->blackHole(noi);
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::CannotInitializeNodeWithData, status);
@@ -571,7 +571,7 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h1", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 0 <<
                                                                    "set" << "rs0" <<
@@ -582,7 +582,7 @@ namespace {
                 _net->blackHole(noi);
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NewReplicaSetConfigurationIncompatible, status);
@@ -623,18 +623,18 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h2", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 0 << "mismatch" << true),
                                                               Milliseconds(8))));
             }
             else {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(ErrorCodes::NoSuchKey, "No response"));
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NewReplicaSetConfigurationIncompatible, status);
@@ -677,18 +677,18 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h1", 1) || request.target == HostAndPort("h5", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 1),
                                                               Milliseconds(8))));
             }
             else {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(ErrorCodes::NoSuchKey, "No response"));
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NodeNotFound, status);
@@ -730,18 +730,18 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h5", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 1),
                                                               Milliseconds(8))));
             }
             else {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(ErrorCodes::NoSuchKey, "No response"));
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         Status status = waitForQuorumCheck();
         ASSERT_EQUALS(ErrorCodes::NodeNotFound, status);
@@ -779,7 +779,7 @@ namespace {
                 "Already saw " << request.target.toString();
             if (request.target == HostAndPort("h1", 1) || request.target == HostAndPort("h2", 1)) {
                 _net->scheduleResponse(noi,
-                                       startDate + 10,
+                                       startDate + Milliseconds(10),
                                        ResponseStatus(RemoteCommandResponse(
                                                               BSON("ok" << 1),
                                                               Milliseconds(8))));
@@ -788,7 +788,7 @@ namespace {
                 _net->blackHole(noi);
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
         ASSERT_OK(waitForQuorumCheck());
     }
diff --git a/src/mongo/db/repl/data_replicator.cpp b/src/mongo/db/repl/data_replicator.cpp
index 4d1964c59ae..288f218c19f 100644
--- a/src/mongo/db/repl/data_replicator.cpp
+++ b/src/mongo/db/repl/data_replicator.cpp
@@ -61,7 +61,7 @@ namespace repl {
     MONGO_FP_DECLARE(failInitialSyncWithBadHost);
 
     namespace {
-        int NoSyncSourceRetryDelayMS = 4000;
+        const Milliseconds NoSyncSourceRetryDelayMS{4000};
 
         std::string toString(DataReplicatiorState s) {
             switch (s) {
@@ -499,7 +499,7 @@ namespace repl {
 
             if (status.code() == ErrorCodes::InvalidSyncSource) {
                 // Error, sync source
-                Date_t until = 0;
+                Date_t until{};
                 _replCoord->blacklistSyncSource(_syncSource, until);
                 _syncSource = HostAndPort();
             }
diff --git a/src/mongo/db/repl/data_replicator_test.cpp b/src/mongo/db/repl/data_replicator_test.cpp
index db8ed712737..8fc727c7b38 100644
--- a/src/mongo/db/repl/data_replicator_test.cpp
+++ b/src/mongo/db/repl/data_replicator_test.cpp
@@ -84,7 +84,7 @@ namespace {
         void scheduleNetworkResponse(const BSONObj& obj) {
             NetworkInterfaceMock* net = getNet();
             ASSERT_TRUE(net->hasReadyRequests());
-            ReplicationExecutor::Milliseconds millis(0);
+            Milliseconds millis(0);
             RemoteCommandResponse response(obj, millis);
             ReplicationExecutor::ResponseStatus responseStatus(response);
             net->scheduleResponse(net->getNextReadyRequest(), net->now(), responseStatus);
diff --git a/src/mongo/db/repl/elect_cmd_runner_test.cpp b/src/mongo/db/repl/elect_cmd_runner_test.cpp
index ef9751dc084..f4d4c913bf1 100644
--- a/src/mongo/db/repl/elect_cmd_runner_test.cpp
+++ b/src/mongo/db/repl/elect_cmd_runner_test.cpp
@@ -199,15 +199,15 @@ namespace {
         ASSERT_EQUALS(stripRound(electRequest), stripRound(noi->getRequest().cmdObj));
         ASSERT_EQUALS(HostAndPort("h1"), noi->getRequest().target);
         _net->scheduleResponse(noi,
-                               startDate + 10,
+                               startDate + Milliseconds(10),
                                ResponseStatus(RemoteCommandResponse(
                                                       BSON("ok" << 1 <<
                                                            "vote" << 1 <<
                                                            "round" << 380865962699346850ll),
                                                       Milliseconds(8))));
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitForTest();
         ASSERT_EQUALS(electCmdRunner.getReceivedVotes(), 2);
     }
diff --git a/src/mongo/db/repl/fetcher_test.cpp b/src/mongo/db/repl/fetcher_test.cpp
index 427f888ff50..c78ade64872 100644
--- a/src/mongo/db/repl/fetcher_test.cpp
+++ b/src/mongo/db/repl/fetcher_test.cpp
@@ -109,7 +109,7 @@ namespace {
     void FetcherTest::scheduleNetworkResponse(const BSONObj& obj) {
         NetworkInterfaceMock* net = getNet();
         ASSERT_TRUE(net->hasReadyRequests());
-        ReplicationExecutor::Milliseconds millis(0);
+        Milliseconds millis(0);
         RemoteCommandResponse response(obj, millis);
         ReplicationExecutor::ResponseStatus responseStatus(response);
         net->scheduleResponse(net->getNextReadyRequest(), net->now(), responseStatus);
diff --git a/src/mongo/db/repl/freshness_checker.cpp b/src/mongo/db/repl/freshness_checker.cpp
index 2c5ef4872b8..17a501f2ce4 100644
--- a/src/mongo/db/repl/freshness_checker.cpp
+++ b/src/mongo/db/repl/freshness_checker.cpp
@@ -88,7 +88,7 @@ namespace repl {
         BSONObjBuilder freshCmdBuilder;
         freshCmdBuilder.append("replSetFresh", 1);
         freshCmdBuilder.append("set", _rsConfig.getReplSetName());
-        freshCmdBuilder.append("opTime", Date_t(_lastOpTimeApplied.asULL()));
+        freshCmdBuilder.append("opTime", Date_t::fromMillisSinceEpoch(_lastOpTimeApplied.asLL()));
         freshCmdBuilder.append("who", selfConfig.getHostAndPort().toString());
         freshCmdBuilder.appendIntOrLL("cfgver", _rsConfig.getConfigVersion());
         freshCmdBuilder.append("id", selfConfig.getId());
diff --git a/src/mongo/db/repl/freshness_checker_test.cpp b/src/mongo/db/repl/freshness_checker_test.cpp
index 08766cfd7ca..6dbf3e666bc 100644
--- a/src/mongo/db/repl/freshness_checker_test.cpp
+++ b/src/mongo/db/repl/freshness_checker_test.cpp
@@ -186,7 +186,7 @@ namespace {
             ASSERT_EQUALS(HostAndPort("h1"), noi->getRequest().target);
             _net->scheduleResponse(
                     noi,
-                    startDate + 10,
+                    startDate + Milliseconds(10),
                     ResponseStatus(RemoteCommandResponse(
                                            BSON("ok" << 1 <<
                                                 "id" << 2 <<
@@ -196,9 +196,9 @@ namespace {
                                                 "opTime" << Date_t(Timestamp(0,0).asULL())),
                                            Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
         ASSERT_EQUALS(shouldAbortElection(), FreshnessChecker::FreshnessTie);
     }
@@ -254,7 +254,7 @@ namespace {
             ASSERT_EQUALS(HostAndPort("h1"), noi->getRequest().target);
             _net->scheduleResponse(
                     noi,
-                    startDate + 10,
+                    startDate + Milliseconds(10),
                     ResponseStatus(RemoteCommandResponse(
                                            BSON("ok" << 1 <<
                                                 "id" << 2 <<
@@ -265,9 +265,9 @@ namespace {
                                                 "opTime" << Date_t(Timestamp(0,0).asULL())),
                                            Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
 
         stopCapturingLogMessages();
@@ -300,7 +300,7 @@ namespace {
             ASSERT_EQUALS(HostAndPort("h1"), noi->getRequest().target);
             _net->scheduleResponse(
                     noi,
-                    startDate + 10,
+                    startDate + Milliseconds(10),
                     ResponseStatus(RemoteCommandResponse(
                                            BSON("ok" << 1 <<
                                                 "id" << 2 <<
@@ -310,9 +310,9 @@ namespace {
                                                 "opTime" << Date_t(Timestamp(10,0).asULL())),
                                            Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
 
         stopCapturingLogMessages();
@@ -344,7 +344,7 @@ namespace {
             ASSERT_EQUALS(HostAndPort("h1"), noi->getRequest().target);
             _net->scheduleResponse(
                     noi,
-                    startDate + 10,
+                    startDate + Milliseconds(10),
                     ResponseStatus(RemoteCommandResponse(
                                            BSON("ok" << 1 <<
                                                 "id" << 2 <<
@@ -354,9 +354,9 @@ namespace {
                                                 "opTime" << 3),
                                            Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
 
         stopCapturingLogMessages();
@@ -391,7 +391,7 @@ namespace {
             ASSERT_EQUALS(HostAndPort("h1"), noi->getRequest().target);
             _net->scheduleResponse(
                     noi,
-                    startDate + 10,
+                    startDate + Milliseconds(10),
                     ResponseStatus(RemoteCommandResponse(
                                            BSON("ok" << 1 <<
                                                 "id" << 2 <<
@@ -403,9 +403,9 @@ namespace {
                                                 "opTime" << Date_t(Timestamp(0,0).asULL())),
                                            Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
 
         stopCapturingLogMessages();
@@ -466,14 +466,14 @@ namespace {
             }
             _net->scheduleResponse(
                     noi,
-                    startDate + 10,
+                    startDate + Milliseconds(10),
                     ResponseStatus(RemoteCommandResponse(
                                            responseBuilder.obj(),
                                            Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
         stopCapturingLogMessages();
         ASSERT_EQUALS(shouldAbortElection(), FreshnessChecker::FresherNodeFound);
@@ -527,7 +527,7 @@ namespace {
                     "opTime" << Date_t(Timestamp(20,0).asULL());
                 _net->scheduleResponse(
                         noi,
-                        startDate + 20,
+                        startDate + Milliseconds(20),
                         ResponseStatus(RemoteCommandResponse(
                                                responseBuilder.obj(),
                                                Milliseconds(8))));
@@ -542,17 +542,17 @@ namespace {
                     "opTime" << Date_t(Timestamp(10,0).asULL());
                 _net->scheduleResponse(
                         noi,
-                        startDate + 10,
+                        startDate + Milliseconds(10),
                         ResponseStatus(RemoteCommandResponse(
                                                responseBuilder.obj(),
                                                Milliseconds(8))));
             }
         }
-        _net->runUntil(startDate + 10);
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        _net->runUntil(startDate + Milliseconds(10));
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         ASSERT_EQUALS(0, countLogLinesContaining("not electing self, we are not freshest"));
-        _net->runUntil(startDate + 20);
-        ASSERT_EQUALS(startDate + 20, _net->now());
+        _net->runUntil(startDate + Milliseconds(20));
+        ASSERT_EQUALS(startDate + Milliseconds(20), _net->now());
         _net->exitNetwork();
         waitOnChecker();
         stopCapturingLogMessages();
@@ -606,14 +606,14 @@ namespace {
             }
             _net->scheduleResponse(
                     noi,
-                    startDate + 10,
+                    startDate + Milliseconds(10),
                     ResponseStatus(RemoteCommandResponse(
                                            responseBuilder.obj(),
                                            Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
         stopCapturingLogMessages();
         ASSERT_EQUALS(shouldAbortElection(), FreshnessChecker::FresherNodeFound);
@@ -666,14 +666,14 @@ namespace {
             }
             _net->scheduleResponse(
                     noi,
-                    startDate + 10,
+                    startDate + Milliseconds(10),
                     ResponseStatus(RemoteCommandResponse(
                                            responseBuilder.obj(),
                                            Milliseconds(8))));
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
         stopCapturingLogMessages();
         ASSERT_EQUALS(shouldAbortElection(), FreshnessChecker::FresherNodeFound);
@@ -730,7 +730,7 @@ namespace {
                     "opTime" << Date_t(Timestamp(10,0).asULL());
                 _net->scheduleResponse(
                         noi,
-                        startDate + 20,
+                        startDate + Milliseconds(20),
                         ResponseStatus(RemoteCommandResponse(
                                                responseBuilder.obj(),
                                                Milliseconds(8))));
@@ -745,18 +745,18 @@ namespace {
                     "opTime" << Date_t(Timestamp(10,0).asULL());
                 _net->scheduleResponse(
                         noi,
-                        startDate + 10,
+                        startDate + Milliseconds(10),
                         ResponseStatus(RemoteCommandResponse(
                                                responseBuilder.obj(),
                                                Milliseconds(8))));
             }
         }
-        _net->runUntil(startDate + 10);
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        _net->runUntil(startDate + Milliseconds(10));
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         ASSERT_EQUALS(0, countLogLinesContaining("not electing self, h4:27017 would veto with '"
                                                  "errmsg: \"I'd rather you didn't\"'"));
-        _net->runUntil(startDate + 20);
-        ASSERT_EQUALS(startDate + 20, _net->now());
+        _net->runUntil(startDate + Milliseconds(20));
+        ASSERT_EQUALS(startDate + Milliseconds(20), _net->now());
         _net->exitNetwork();
         waitOnChecker();
         stopCapturingLogMessages();
@@ -799,7 +799,7 @@ namespace {
             if (target.host() == "h2" || target.host() == "h3") {
                 _net->scheduleResponse(
                         noi,
-                        startDate + 10,
+                        startDate + Milliseconds(10),
                         ResponseStatus(ErrorCodes::NoSuchKey, "No response"));
             }
             else {
@@ -813,15 +813,15 @@ namespace {
                     "opTime" << Date_t(Timestamp(0,0).asULL());
                 _net->scheduleResponse(
                         noi,
-                        startDate + 10,
+                        startDate + Milliseconds(10),
                         ResponseStatus(RemoteCommandResponse(
                                                responseBuilder.obj(),
                                                Milliseconds(8))));
             }
         }
-        _net->runUntil(startDate + 10);
+        _net->runUntil(startDate + Milliseconds(10));
         _net->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, _net->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), _net->now());
         waitOnChecker();
         ASSERT_EQUALS(shouldAbortElection(),FreshnessChecker::None);
     }
diff --git a/src/mongo/db/repl/heartbeat_response_action.cpp b/src/mongo/db/repl/heartbeat_response_action.cpp
index 4f26bc2953e..49ed33c4780 100644
--- a/src/mongo/db/repl/heartbeat_response_action.cpp
+++ b/src/mongo/db/repl/heartbeat_response_action.cpp
@@ -63,11 +63,7 @@ namespace repl {
         return result;
     }
 
-    HeartbeatResponseAction::HeartbeatResponseAction() :
-        _action(NoAction),
-        _primaryIndex(-1),
-        _nextHeartbeatStartDate(0) {
-    }
+    HeartbeatResponseAction::HeartbeatResponseAction() : _action(NoAction), _primaryIndex(-1) {}
 
     void HeartbeatResponseAction::setNextHeartbeatStartDate(Date_t when) {
         _nextHeartbeatStartDate = when;
diff --git a/src/mongo/db/repl/is_master_response.cpp b/src/mongo/db/repl/is_master_response.cpp
index a789fd7b6dd..ab38c295d14 100644
--- a/src/mongo/db/repl/is_master_response.cpp
+++ b/src/mongo/db/repl/is_master_response.cpp
@@ -152,7 +152,7 @@ namespace {
         if (_buildIndexesSet)
             builder->append(kBuildIndexesFieldName, _buildIndexes);
         if (_slaveDelaySet)
-            builder->append(kSlaveDelayFieldName, _slaveDelay.total_seconds());
+            builder->appendIntOrLL(kSlaveDelayFieldName, durationCount<Seconds>(_slaveDelay));
         if (_tagsSet) {
             BSONObjBuilder tags(builder->subobjStart(kTagsFieldName));
             for (unordered_map<std::string, std::string>::const_iterator it = _tags.begin();
diff --git a/src/mongo/db/repl/master_slave.cpp b/src/mongo/db/repl/master_slave.cpp
index 7d9624f8849..9ebf1ce6cf1 100644
--- a/src/mongo/db/repl/master_slave.cpp
+++ b/src/mongo/db/repl/master_slave.cpp
@@ -326,7 +326,7 @@ namespace repl {
                 DBDirectClient c(txn);
                 BSONObj op = c.findOne( "local.oplog.$main", QUERY( "op" << NE << "n" ).sort( BSON( "$natural" << -1 ) ) );
                 if ( !op.isEmpty() ) {
-                    tmp.syncedTo = op[ "ts" ].date();
+                    tmp.syncedTo = op[ "ts" ].timestamp();
                 }
             }
             addSourceToList(txn, v, tmp, old);
@@ -541,7 +541,7 @@ namespace repl {
             return true;   
         }
         BSONElement ts = op.getField( "ts" );
-        if ( ( ts.type() == Date || ts.type() == bsonTimestamp ) && ___databaseIgnorer.ignoreAt( db, ts.date() ) ) {
+        if ( ( ts.type() == Date || ts.type() == bsonTimestamp ) && ___databaseIgnorer.ignoreAt( db, ts.timestamp() ) ) {
             // Database is ignored due to a previous indication that it is
             // missing from master after optime "ts".
             return false;   
diff --git a/src/mongo/db/repl/member_config.cpp b/src/mongo/db/repl/member_config.cpp
index 6f3bcf40501..02711adedd3 100644
--- a/src/mongo/db/repl/member_config.cpp
+++ b/src/mongo/db/repl/member_config.cpp
@@ -259,7 +259,7 @@ namespace {
         }
         if (_slaveDelay < Seconds(0) || _slaveDelay > kMaxSlaveDelay) {
             return Status(ErrorCodes::BadValue, str::stream() << kSlaveDelayFieldName <<
-                          " field value of " << _slaveDelay.total_seconds() <<
+                          " field value of " << durationCount<Seconds>(_slaveDelay) <<
                           " seconds is out of range");
         }
         if (_slaveDelay > Seconds(0) && _priority != 0) {
@@ -310,7 +310,7 @@ namespace {
         }
         tags.done();
 
-        configBuilder.append("slaveDelay", _slaveDelay.total_seconds());
+        configBuilder.append("slaveDelay", durationCount<Seconds>(_slaveDelay));
         configBuilder.append("votes", getNumVotes());
         return configBuilder.obj();
     }
diff --git a/src/mongo/db/repl/member_config_test.cpp b/src/mongo/db/repl/member_config_test.cpp
index 9d3a0f7b276..e69b17c237b 100644
--- a/src/mongo/db/repl/member_config_test.cpp
+++ b/src/mongo/db/repl/member_config_test.cpp
@@ -46,7 +46,7 @@ namespace {
         ASSERT_EQUALS(0, mc.getId());
         ASSERT_EQUALS(HostAndPort("localhost", 12345), mc.getHostAndPort());
         ASSERT_EQUALS(1.0, mc.getPriority());
-        ASSERT_EQUALS(0, mc.getSlaveDelay().total_seconds());
+        ASSERT_EQUALS(Seconds(0), mc.getSlaveDelay());
         ASSERT_TRUE(mc.isVoter());
         ASSERT_FALSE(mc.isHidden());
         ASSERT_FALSE(mc.isArbiter());
@@ -188,7 +188,7 @@ namespace {
         MemberConfig mc;
         ASSERT_OK(mc.initialize(BSON("_id" << 0 << "host" << "h" << "slaveDelay" << 100),
                                 &tagConfig));
-        ASSERT_EQUALS(100, mc.getSlaveDelay().total_seconds());
+        ASSERT_EQUALS(Seconds(100), mc.getSlaveDelay());
     }
 
     TEST(MemberConfig, ParseTags) {
diff --git a/src/mongo/db/repl/member_heartbeat_data.cpp b/src/mongo/db/repl/member_heartbeat_data.cpp
index 5ae8f1fbffc..c4c99f5bd28 100644
--- a/src/mongo/db/repl/member_heartbeat_data.cpp
+++ b/src/mongo/db/repl/member_heartbeat_data.cpp
@@ -41,9 +41,6 @@ namespace repl {
 
     MemberHeartbeatData::MemberHeartbeatData() :
         _health(-1),
-        _upSince(0),
-        _lastHeartbeat(0),
-        _lastHeartbeatRecv(0),
         _authIssue(false) {
 
         _lastResponse.setState(MemberState::RS_UNKNOWN);
@@ -55,7 +52,7 @@ namespace repl {
                                           const HostAndPort& host,
                                           ReplSetHeartbeatResponse hbResponse) {
         _health = 1;
-        if (_upSince == 0) {
+        if (_upSince == Date_t()) {
             _upSince = now;
         }
         _authIssue = false;
@@ -82,7 +79,7 @@ namespace repl {
     void MemberHeartbeatData::setDownValues(Date_t now, const std::string& heartbeatMessage) {
 
         _health = 0;
-        _upSince = 0;
+        _upSince = Date_t();
         _lastHeartbeat = now;
         _authIssue = false;
 
@@ -96,7 +93,7 @@ namespace repl {
 
     void MemberHeartbeatData::setAuthIssue(Date_t now) {
         _health = 0;  // set health to 0 so that this doesn't count towards majority.
-        _upSince = 0;
+        _upSince = Date_t();
         _lastHeartbeat = now;
         _authIssue = true;
 
diff --git a/src/mongo/db/repl/network_interface_impl.cpp b/src/mongo/db/repl/network_interface_impl.cpp
index 3dd08e51a14..69ab9dc921e 100644
--- a/src/mongo/db/repl/network_interface_impl.cpp
+++ b/src/mongo/db/repl/network_interface_impl.cpp
@@ -159,7 +159,7 @@ namespace {
             if (waitTime <= Milliseconds(0)) {
                 break;
             }
-            _isExecutorRunnableCondition.timed_wait(lk, waitTime);
+            _isExecutorRunnableCondition.wait_for(lk, waitTime);
         }
         _isExecutorRunnable = false;
     }
@@ -184,13 +184,13 @@ namespace {
                 if (_threads.size() > kMinThreads) {
                     const Date_t nowDate = now();
                     const Date_t nextThreadRetirementDate =
-                        _lastFullUtilizationDate + kMaxIdleThreadAge.total_milliseconds();
+                        _lastFullUtilizationDate + kMaxIdleThreadAge;
                     if (nowDate > nextThreadRetirementDate) {
                         _lastFullUtilizationDate = nowDate;
                         break;
                     }
                 }
-                _hasPending.timed_wait(lk, kMaxIdleThreadAge);
+                _hasPending.wait_for(lk, kMaxIdleThreadAge);
                 continue;
             }
             CommandData todo = _pending.front();
@@ -243,7 +243,7 @@ namespace {
             _startNewNetworkThread_inlock();
         }
         if (_numIdleThreads <= _pending.size()) {
-            _lastFullUtilizationDate = curTimeMillis64();
+            _lastFullUtilizationDate = Date_t::now();
         }
         _hasPending.notify_one();
     }
@@ -270,7 +270,7 @@ namespace {
     }
 
     Date_t NetworkInterfaceImpl::now() {
-        return curTimeMillis64();
+        return Date_t::now();
     }
 
     OperationContext* NetworkInterfaceImpl::createOperationContext() {
diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index 00bd96fe12a..717ca32a578 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -886,7 +886,7 @@ namespace {
 
         if (!lastOp.isEmpty()) {
             LOG(1) << "replSet setting last OpTime";
-            setNewOptime(lastOp[ "ts" ].date());
+            setNewOptime(lastOp[ "ts" ].timestamp());
         }
     }
 
diff --git a/src/mongo/db/repl/oplogreader.cpp b/src/mongo/db/repl/oplogreader.cpp
index 5a0e1054d12..bea0484fc44 100644
--- a/src/mongo/db/repl/oplogreader.cpp
+++ b/src/mongo/db/repl/oplogreader.cpp
@@ -144,7 +144,7 @@ namespace repl {
     void OplogReader::connectToSyncSource(OperationContext* txn,
                                           Timestamp lastOpTimeFetched,
                                           ReplicationCoordinator* replCoord) {
-        const Timestamp sentinel(Milliseconds(curTimeMillis64()).total_seconds(), 0);
+        const Timestamp sentinel(duration_cast<Seconds>(Milliseconds(curTimeMillis64())), 0);
         Timestamp oldestOpTimeSeen = sentinel;
 
         invariant(conn() == NULL);
@@ -182,7 +182,7 @@ namespace repl {
                 LOG(2) << "can't connect to " << candidate.toString() <<
                     " to read operations";
                 resetConnection();
-                replCoord->blacklistSyncSource(candidate, Date_t(curTimeMillis64() + 10*1000));
+                replCoord->blacklistSyncSource(candidate, Date_t::now() + Seconds(10));
                 continue;
             }
             // Read the first (oldest) op and confirm that it's not newer than our last
@@ -193,8 +193,7 @@ namespace repl {
                 // This member's got a bad op in its oplog.
                 warning() << "oplog invalid format on node " << candidate.toString();
                 resetConnection();
-                replCoord->blacklistSyncSource(candidate, 
-                                               Date_t(curTimeMillis64() + 600*1000));
+                replCoord->blacklistSyncSource(candidate, Date_t::now() + Minutes(10));
                 continue;
             }
             Timestamp remoteOldOpTime = tsElem.timestamp();
@@ -202,8 +201,7 @@ namespace repl {
             if (lastOpTimeFetched < remoteOldOpTime) {
                 // We're too stale to use this sync source.
                 resetConnection();
-                replCoord->blacklistSyncSource(candidate, 
-                                               Date_t(curTimeMillis64() + 600*1000));
+                replCoord->blacklistSyncSource(candidate, Date_t::now() + Minutes(10));
                 if (oldestOpTimeSeen > remoteOldOpTime) {
                     warning() << "we are too stale to use " << candidate.toString() << 
                         " as a sync source";
diff --git a/src/mongo/db/repl/read_after_optime_args_test.cpp b/src/mongo/db/repl/read_after_optime_args_test.cpp
index d780500d9c2..557767c2886 100644
--- a/src/mongo/db/repl/read_after_optime_args_test.cpp
+++ b/src/mongo/db/repl/read_after_optime_args_test.cpp
@@ -46,7 +46,7 @@ namespace {
 
         ASSERT_EQ(Timestamp(20, 30), readAfterOpTime.getOpTime().getTimestamp());
         ASSERT_EQ(2, readAfterOpTime.getOpTime().getTerm());
-        ASSERT_EQ(100, readAfterOpTime.getTimeout().total_milliseconds());
+        ASSERT_EQ(Milliseconds(100), readAfterOpTime.getTimeout());
     }
 
     TEST(ReadAfterParse, Empty) {
@@ -54,7 +54,7 @@ namespace {
         ASSERT_OK(readAfterOpTime.initialize(BSON("find" << "test")));
 
         ASSERT(readAfterOpTime.getOpTime().getTimestamp().isNull());
-        ASSERT_EQ(0, readAfterOpTime.getTimeout().total_milliseconds());
+        ASSERT_EQ(Milliseconds::zero(), readAfterOpTime.getTimeout());
     }
 
     TEST(ReadAfterParse, BadRootType) {
@@ -133,7 +133,7 @@ namespace {
 
         ASSERT_EQ(Timestamp(1, 0), readAfterOpTime.getOpTime().getTimestamp());
         ASSERT_EQ(2, readAfterOpTime.getOpTime().getTerm());
-        ASSERT_EQ(0, readAfterOpTime.getTimeout().total_milliseconds());
+        ASSERT_EQ(Milliseconds::zero(), readAfterOpTime.getTimeout());
     }
 
     TEST(ReadAfterParse, BadTimeoutType) {
@@ -170,7 +170,7 @@ namespace {
 
         ASSERT_EQ(Timestamp(20, 30), readAfterOpTime.getOpTime().getTimestamp());
         ASSERT_EQ(2, readAfterOpTime.getOpTime().getTerm());
-        ASSERT_EQ(0, readAfterOpTime.getTimeout().total_milliseconds());
+        ASSERT_EQ(Milliseconds::zero(), readAfterOpTime.getTimeout());
     }
 
 } // unnamed namespace
diff --git a/src/mongo/db/repl/read_after_optime_response.cpp b/src/mongo/db/repl/read_after_optime_response.cpp
index 7caffe09a96..3a6d5fc9962 100644
--- a/src/mongo/db/repl/read_after_optime_response.cpp
+++ b/src/mongo/db/repl/read_after_optime_response.cpp
@@ -42,7 +42,7 @@ namespace repl {
     const string ReadAfterOpTimeResponse::kWaitedMSFieldName("waitedMS");
 
     ReadAfterOpTimeResponse::ReadAfterOpTimeResponse(Status status):
-        ReadAfterOpTimeResponse(status, boost::posix_time::milliseconds(0), false) {
+        ReadAfterOpTimeResponse(status, stdx::chrono::milliseconds(0), false) {
     }
 
     ReadAfterOpTimeResponse::ReadAfterOpTimeResponse():
@@ -50,12 +50,12 @@ namespace repl {
     }
 
     ReadAfterOpTimeResponse::ReadAfterOpTimeResponse(Status status,
-                                                     boost::posix_time::milliseconds duration):
+                                                     stdx::chrono::milliseconds duration):
         ReadAfterOpTimeResponse(status, duration, true) {
     }
 
     ReadAfterOpTimeResponse::ReadAfterOpTimeResponse(Status status,
-                                                     boost::posix_time::milliseconds duration,
+                                                     stdx::chrono::milliseconds duration,
                                                      bool waited):
         _waited(waited),
         _duration(duration),
@@ -67,15 +67,14 @@ namespace repl {
             return;
         }
 
-        builder->append(kWaitedMSFieldName,
-                        static_cast<long long>(_duration.total_milliseconds()));
+        builder->append(kWaitedMSFieldName, durationCount<Milliseconds>(_duration));
     }
 
     bool ReadAfterOpTimeResponse::didWait() const {
         return _waited;
     }
 
-    boost::posix_time::milliseconds ReadAfterOpTimeResponse::getDuration() const {
+    stdx::chrono::milliseconds ReadAfterOpTimeResponse::getDuration() const {
         return _duration;
     }
 
diff --git a/src/mongo/db/repl/read_after_optime_response.h b/src/mongo/db/repl/read_after_optime_response.h
index b906dc196d4..33163131363 100644
--- a/src/mongo/db/repl/read_after_optime_response.h
+++ b/src/mongo/db/repl/read_after_optime_response.h
@@ -28,10 +28,10 @@
 
 #pragma once
 
-#include <boost/date_time/posix_time/posix_time_types.hpp>
 #include <string>
 
 #include "mongo/base/status.h"
+#include "mongo/stdx/chrono.h"
 
 namespace mongo {
 
@@ -56,7 +56,7 @@ namespace repl {
         /**
          * Constructs a response with wait set to true along with the given parameters.
          */
-        ReadAfterOpTimeResponse(Status status, boost::posix_time::milliseconds duration);
+        ReadAfterOpTimeResponse(Status status, stdx::chrono::milliseconds duration);
 
         /**
          * Appends to the builder the timeout and duration info if didWait() is true.
@@ -70,7 +70,7 @@ namespace repl {
          * Returns the amount of duration waiting for opTime to pass.
          * Valid only if didWait is true.
          */
-        boost::posix_time::milliseconds getDuration() const;
+        stdx::chrono::milliseconds getDuration() const;
 
         /**
          * Returns more details about an error if it occurred.
@@ -79,11 +79,11 @@ namespace repl {
 
     private:
         ReadAfterOpTimeResponse(Status status,
-                                boost::posix_time::milliseconds duration,
+                                stdx::chrono::milliseconds duration,
                                 bool waited);
 
         bool _waited;
-        boost::posix_time::milliseconds _duration;
+        stdx::chrono::milliseconds _duration;
         Status _status;
     };
 
diff --git a/src/mongo/db/repl/read_after_optime_response_test.cpp b/src/mongo/db/repl/read_after_optime_response_test.cpp
index a30824a57b8..09d70204255 100644
--- a/src/mongo/db/repl/read_after_optime_response_test.cpp
+++ b/src/mongo/db/repl/read_after_optime_response_test.cpp
@@ -62,10 +62,10 @@ namespace {
 
     TEST(ReadAfterResponse, WaitedWithDuration) {
         ReadAfterOpTimeResponse response(Status(ErrorCodes::InternalError, "test"),
-                                         boost::posix_time::milliseconds(7));
+                                         stdx::chrono::milliseconds(7));
 
         ASSERT_TRUE(response.didWait());
-        ASSERT_EQUALS(7, response.getDuration().total_milliseconds());
+        ASSERT_EQUALS(Milliseconds(7), response.getDuration());
         ASSERT_EQ(ErrorCodes::InternalError, response.getStatus().code());
 
         BSONObjBuilder builder;
diff --git a/src/mongo/db/repl/repl_set_heartbeat_response.cpp b/src/mongo/db/repl/repl_set_heartbeat_response.cpp
index 8dac175ddf9..8ea4bd0028f 100644
--- a/src/mongo/db/repl/repl_set_heartbeat_response.cpp
+++ b/src/mongo/db/repl/repl_set_heartbeat_response.cpp
@@ -90,13 +90,14 @@ namespace {
 
         builder->append(kOkFieldName, 1.0);
         if (_opTimeSet) {
-            builder->appendDate(kOpTimeFieldName, _opTime.asULL());
+            builder->appendDate(kOpTimeFieldName, Date_t::fromMillisSinceEpoch(_opTime.asLL()));
         }
         if (_timeSet) {
-            *builder << kTimeFieldName << _time.total_seconds();
+            *builder << kTimeFieldName << durationCount<Seconds>(_time);
         }
         if (_electionTimeSet) {
-            builder->appendDate(kElectionTimeFieldName, _electionTime.asULL());
+            builder->appendDate(kElectionTimeFieldName,
+                                Date_t::fromMillisSinceEpoch(_electionTime.asLL()));
         }
         if (_configSet) {
             *builder << kConfigFieldName << _config.toBSON();
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 05e634fbc03..76cf0a99448 100644
--- a/src/mongo/db/repl/repl_set_heartbeat_response_test.cpp
+++ b/src/mongo/db/repl/repl_set_heartbeat_response_test.cpp
@@ -201,7 +201,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
 
         hbResponseObj = hbResponse.toBSON();
         ASSERT_EQUALS(fieldsSet, hbResponseObj.nFields());
@@ -234,7 +234,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
         ASSERT_EQUALS(true, hbResponse.isElectable());
 
         hbResponseObj = hbResponse.toBSON();
@@ -270,7 +270,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
 
@@ -309,7 +309,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
 
@@ -349,7 +349,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
 
@@ -391,7 +391,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
 
@@ -434,7 +434,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
 
@@ -477,7 +477,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
 
@@ -520,7 +520,7 @@ namespace {
         ASSERT_EQUALS(1, hbResponse.getVersion());
         ASSERT_EQUALS(Timestamp(10,0), hbResponse.getElectionTime());
         ASSERT_EQUALS(Timestamp(0,10), hbResponse.getOpTime());
-        ASSERT_EQUALS(10, hbResponse.getTime().total_seconds());
+        ASSERT_EQUALS(Seconds(10), hbResponse.getTime());
         ASSERT_EQUALS(true, hbResponse.isElectable());
         ASSERT_EQUALS(config.toBSON().toString(), hbResponse.getConfig().toBSON().toString());
 
diff --git a/src/mongo/db/repl/repl_set_html_summary.cpp b/src/mongo/db/repl/repl_set_html_summary.cpp
index 465bfdeb95e..65524427b4a 100644
--- a/src/mongo/db/repl/repl_set_html_summary.cpp
+++ b/src/mongo/db/repl/repl_set_html_summary.cpp
@@ -68,8 +68,7 @@ namespace {
     }
 
     unsigned int timeDifference(Date_t now, Date_t past) {
-        return static_cast<unsigned int> ((past ?
-                (now - past) / 1000 /* convert millis to secs */ : 0));
+        return static_cast<unsigned int>(past != Date_t() ? durationCount<Seconds>(now - past) : 0);
     }
 
     std::string stateAsHtml(const MemberState& s) {
@@ -174,7 +173,7 @@ namespace {
                 memberTable << td(red(str::stream() << memberHB.getHealth(), !up));
                 const unsigned int uptime = timeDifference(_now, memberHB.getUpSince());
                 memberTable << td(ago(uptime));
-                if (memberHB.getLastHeartbeat() == 0) {
+                if (memberHB.getLastHeartbeat() == Date_t()) {
                     memberTable << td("never");
                 }
                 else {
@@ -191,7 +190,7 @@ namespace {
                     memberTable << td( grey(str::stream() << "(was " << state << ')', true) );
                 }
                 memberTable << td(grey(memberHB.getLastHeartbeatMsg(), !up));
-                memberTable << td(memberHB.getLastHeartbeat() == 0 ?
+                memberTable << td(memberHB.getLastHeartbeat() == Date_t() ?
                         "?" : memberHB.getOpTime().toString());
             }
             memberTable << _tr();
diff --git a/src/mongo/db/repl/replica_set_config.cpp b/src/mongo/db/repl/replica_set_config.cpp
index 1e7c343db7e..dda9e25cf55 100644
--- a/src/mongo/db/repl/replica_set_config.cpp
+++ b/src/mongo/db/repl/replica_set_config.cpp
@@ -274,7 +274,7 @@ namespace {
         if (_heartbeatTimeoutPeriod < Seconds(0)) {
             return Status(ErrorCodes::BadValue, str::stream() << kSettingsFieldName << '.' <<
                           kHeartbeatTimeoutFieldName << " field value must be non-negative, "
-                          "but found " << _heartbeatTimeoutPeriod.total_seconds());
+                          "but found " << _heartbeatTimeoutPeriod.count());
         }
         if (_members.size() > kMaxMembers || _members.empty()) {
             return Status(ErrorCodes::BadValue, str::stream() <<
@@ -539,7 +539,7 @@ namespace {
 
         BSONObjBuilder settingsBuilder(configBuilder.subobjStart(kSettingsFieldName));
         settingsBuilder.append(kChainingAllowedFieldName, _chainingAllowed);
-        settingsBuilder.append(kHeartbeatTimeoutFieldName, _heartbeatTimeoutPeriod.total_seconds());
+        settingsBuilder.appendIntOrLL(kHeartbeatTimeoutFieldName, _heartbeatTimeoutPeriod.count());
 
         BSONObjBuilder gleModes(settingsBuilder.subobjStart(kGetLastErrorModesFieldName));
         for (StringMap<ReplicaSetTagPattern>::const_iterator mode =
diff --git a/src/mongo/db/repl/replica_set_config.h b/src/mongo/db/repl/replica_set_config.h
index c51ef2ebb40..fcd880705ea 100644
--- a/src/mongo/db/repl/replica_set_config.h
+++ b/src/mongo/db/repl/replica_set_config.h
@@ -161,7 +161,7 @@ namespace repl {
          * Seconds object.
          */
         Milliseconds getHeartbeatTimeoutPeriodMillis() const {
-            return Milliseconds(_heartbeatTimeoutPeriod.total_milliseconds());
+            return _heartbeatTimeoutPeriod;
         }
 
         /**
diff --git a/src/mongo/db/repl/replica_set_config_test.cpp b/src/mongo/db/repl/replica_set_config_test.cpp
index bf2b8f91151..8bc5a247498 100644
--- a/src/mongo/db/repl/replica_set_config_test.cpp
+++ b/src/mongo/db/repl/replica_set_config_test.cpp
@@ -50,7 +50,7 @@ namespace {
         ASSERT_EQUALS(0, config.membersBegin()->getId());
         ASSERT_EQUALS(1, config.getDefaultWriteConcern().wNumNodes);
         ASSERT_EQUALS("", config.getDefaultWriteConcern().wMode);
-        ASSERT_EQUALS(10, config.getHeartbeatTimeoutPeriod().total_seconds());
+        ASSERT_EQUALS(Seconds(10), config.getHeartbeatTimeoutPeriod());
         ASSERT_TRUE(config.isChainingAllowed());
         ASSERT_EQUALS(0, config.getProtocolVersion());
     }
@@ -78,7 +78,7 @@ namespace {
         ASSERT_EQUALS(0, config.getDefaultWriteConcern().wNumNodes);
         ASSERT_EQUALS("majority", config.getDefaultWriteConcern().wMode);
         ASSERT_FALSE(config.isChainingAllowed());
-        ASSERT_EQUALS(120, config.getHeartbeatTimeoutPeriod().total_seconds());
+        ASSERT_EQUALS(Seconds(120), config.getHeartbeatTimeoutPeriod());
         ASSERT_EQUALS(2, config.getProtocolVersion());
     }
 
@@ -603,7 +603,7 @@ namespace {
                                                             "host" << "localhost:12345")) <<
                                "settings" << BSON("heartbeatTimeoutSecs" << 20))));
         ASSERT_OK(config.validate());
-        ASSERT_EQUALS(20, config.getHeartbeatTimeoutPeriod().total_seconds());
+        ASSERT_EQUALS(Seconds(20), config.getHeartbeatTimeoutPeriod());
 
         ASSERT_OK(config.initialize(
                           BSON("_id" << "rs0" <<
diff --git a/src/mongo/db/repl/replication_coordinator.h b/src/mongo/db/repl/replication_coordinator.h
index 9201f4af326..a1a25f5b1f1 100644
--- a/src/mongo/db/repl/replication_coordinator.h
+++ b/src/mongo/db/repl/replication_coordinator.h
@@ -28,7 +28,6 @@
 
 #pragma once
 
-#include <boost/date_time/posix_time/posix_time_types.hpp>
 #include <vector>
 
 #include "mongo/base/disallow_copying.h"
@@ -37,6 +36,7 @@
 #include "mongo/db/repl/repl_settings.h"
 #include "mongo/db/repl/reporter.h"
 #include "mongo/util/net/hostandport.h"
+#include "mongo/util/time_support.h"
 
 namespace mongo {
 
@@ -89,8 +89,6 @@ namespace repl {
 
     public:
 
-        typedef boost::posix_time::milliseconds Milliseconds;
-
         struct StatusAndDuration {
         public:
             Status status;
diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index a83b37b9b76..070487253bd 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -801,8 +801,7 @@ namespace {
         while (ts > _getMyLastOptime_inlock()) {
             Status interruptedStatus = txn->checkForInterruptNoAssert();
             if (!interruptedStatus.isOK()) {
-                return ReadAfterOpTimeResponse(interruptedStatus,
-                        Milliseconds(timer.millis()));
+                return ReadAfterOpTimeResponse(interruptedStatus, Milliseconds(timer.millis()));
             }
 
             if (_inShutdown) {
@@ -811,14 +810,13 @@ namespace {
                         Milliseconds(timer.millis()));
             }
 
-            const auto elapsedMS = timer.millis();
-            if (timeout.total_milliseconds() > 0 &&
-                    elapsedMS > timeout.total_milliseconds()) {
+            const Microseconds elapsedTime{timer.micros()};
+            if (timeout > Microseconds::zero() && elapsedTime > timeout) {
                 return ReadAfterOpTimeResponse(
                         Status(ErrorCodes::ReadAfterOptimeTimeout,
                               str::stream() << "timed out waiting for opTime: "
                                             << ts.toStringPretty()),
-                        Milliseconds(timer.millis()));
+                        duration_cast<Milliseconds>(elapsedTime));
             }
 
             boost::condition_variable condVar;
@@ -828,21 +826,19 @@ namespace {
                                 nullptr, // Don't care about write concern.
                                 &condVar);
 
-            uint64_t maxTimeMicrosRemaining = txn->getRemainingMaxTimeMicros();
-            auto maxTimeMSRemaining = (maxTimeMicrosRemaining == 0) ?
-                    std::numeric_limits<uint64_t>::max() : (maxTimeMicrosRemaining / 1000);
-
-            auto timeoutMSRemaining = (timeout.total_milliseconds() == 0) ?
-                    std::numeric_limits<uint64_t>::max() :
-                    static_cast<uint64_t>(timeout.total_milliseconds() - elapsedMS);
-
-            auto sleepTimeMS = std::min(maxTimeMSRemaining, timeoutMSRemaining);
-
-            if (sleepTimeMS == std::numeric_limits<uint64_t>::max()) {
+            const Microseconds maxTimeMicrosRemaining{txn->getRemainingMaxTimeMicros()};
+            Microseconds waitTime = Microseconds::max();
+            if (maxTimeMicrosRemaining != Microseconds::zero()) {
+                waitTime = maxTimeMicrosRemaining;
+            }
+            if (timeout != Microseconds::zero()) {
+                waitTime = std::min<Microseconds>(timeout - elapsedTime, waitTime);
+            }
+            if (waitTime == Microseconds::max()) {
                 condVar.wait(lock);
             }
             else {
-                condVar.timed_wait(lock, Milliseconds(sleepTimeMS));
+                condVar.wait_for(lock, waitTime);
             }
         }
 
@@ -1142,7 +1138,7 @@ namespace {
                     condVar.wait(*lock);
                 }
                 else {
-                    condVar.timed_wait(*lock, Milliseconds(writeConcern.wTimeout - elapsed));
+                    condVar.wait_for(*lock, Milliseconds(writeConcern.wTimeout - elapsed));
                 }
             } catch (const boost::thread_interrupted&) {}
         }
@@ -1160,8 +1156,8 @@ namespace {
                                                 const Milliseconds& waitTime,
                                                 const Milliseconds& stepdownTime) {
         const Date_t startTime = _replExecutor.now();
-        const Date_t stepDownUntil(startTime.millis + stepdownTime.total_milliseconds());
-        const Date_t waitUntil(startTime.millis + waitTime.total_milliseconds());
+        const Date_t stepDownUntil = startTime + stepdownTime;
+        const Date_t waitUntil = startTime + waitTime;
 
         if (!getMemberState().primary()) {
             // Note this check is inherently racy - it's always possible for the node to
@@ -1177,7 +1173,8 @@ namespace {
         _externalState->killAllUserOperations(txn);
 
         if (lockState == LOCK_WAITING) {
-            lockState = txn->lockState()->lockGlobalComplete(stepdownTime.total_milliseconds());
+            lockState = txn->lockState()->lockGlobalComplete(
+                    durationCount<Milliseconds>(stepdownTime));
             if (lockState == LOCK_TIMEOUT) {
                 return Status(ErrorCodes::ExceededTimeLimit,
                               "Could not acquire the global shared lock within the amount of time "
diff --git a/src/mongo/db/repl/replication_coordinator_impl_elect.cpp b/src/mongo/db/repl/replication_coordinator_impl_elect.cpp
index dffe1e3793f..387f52d2b84 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_elect.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_elect.cpp
@@ -173,9 +173,9 @@ namespace {
                 break;
             case FreshnessChecker::FreshnessTie:
                 if ((_selfIndex != 0) && !_sleptLastElection) {
-                    const long long ms = _replExecutor.nextRandomInt64(1000) + 50;
+                    const auto ms = Milliseconds(_replExecutor.nextRandomInt64(1000) + 50);
                     const Date_t nextCandidateTime = now + ms;
-                    log() << "possible election tie; sleeping " << ms << "ms until " <<
+                    log() << "possible election tie; sleeping " << ms.count() << "ms until " <<
                         dateToISOStringLocal(nextCandidateTime);
                     _topCoord->setElectionSleepUntil(nextCandidateTime);
                     _replExecutor.scheduleWorkAt(
@@ -241,7 +241,7 @@ namespace {
                 " votes, but needed at least " << _rsConfig.getMajorityVoteCount();
             // Suppress ourselves from standing for election again, giving other nodes a chance 
             // to win their elections.
-            const long long ms = _replExecutor.nextRandomInt64(1000) + 50;
+            const auto ms = Milliseconds(_replExecutor.nextRandomInt64(1000) + 50);
             const Date_t now(_replExecutor.now());
             const Date_t nextCandidateTime = now + ms;
             log() << "waiting until " << nextCandidateTime << " before standing for election again";
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 db4104ed761..29add436720 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_elect_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_elect_test.cpp
@@ -347,7 +347,7 @@ namespace {
         BSONObjBuilder respObj2;
         respObj2 << "ok" << 1;
         hbResp2.addToBSON(&respObj2);
-        net->runUntil(net->now() + 10*1000); // run until we've sent a heartbeat request
+        net->runUntil(net->now() + Seconds(10)); // run until we've sent a heartbeat request
         const NetworkInterfaceMock::NetworkOperationIterator noi2 = net->getNextReadyRequest();
         net->scheduleResponse(noi2, net->now(), makeResponseStatus(respObj2.obj()));
         net->runReadyNetworkOperations();
diff --git a/src/mongo/db/repl/replication_coordinator_impl_heartbeat_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_heartbeat_test.cpp
index 30c564284b1..0dec8c5b1a6 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_heartbeat_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_heartbeat_test.cpp
@@ -115,8 +115,10 @@ namespace {
         BSONObjBuilder responseBuilder;
         responseBuilder << "ok" << 1;
         hbResp.addToBSON(&responseBuilder);
-        net->scheduleResponse(noi, startDate + 200, makeResponseStatus(responseBuilder.obj()));
-        assertRunUntil(startDate + 200);
+        net->scheduleResponse(noi,
+                              startDate + Milliseconds(200),
+                              makeResponseStatus(responseBuilder.obj()));
+        assertRunUntil(startDate + Milliseconds(200));
 
         // Because the new config is stored using an out-of-band thread, we need to perform some
         // extra synchronization to let the executor finish the heartbeat reconfig.  We know that
@@ -174,8 +176,10 @@ namespace {
         BSONObjBuilder responseBuilder;
         responseBuilder << "ok" << 1;
         hbResp.addToBSON(&responseBuilder);
-        net->scheduleResponse(noi, startDate + 200, makeResponseStatus(responseBuilder.obj()));
-        assertRunUntil(startDate + 2200);
+        net->scheduleResponse(noi,
+                              startDate + Milliseconds(200),
+                              makeResponseStatus(responseBuilder.obj()));
+        assertRunUntil(startDate + Milliseconds(2200));
 
         // Because the new config is stored using an out-of-band thread, we need to perform some
         // extra synchronization to let the executor finish the heartbeat reconfig.  We know that
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 086a574d630..5b438741b29 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp
@@ -415,7 +415,7 @@ namespace {
         BSONObjBuilder respObj2;
         respObj2 << "ok" << 1;
         hbResp2.addToBSON(&respObj2);
-        net->runUntil(net->now() + 10*1000); // run until we've sent a heartbeat request
+        net->runUntil(net->now() + Seconds(10)); // run until we've sent a heartbeat request
         const NetworkInterfaceMock::NetworkOperationIterator noi2 = net->getNextReadyRequest();
         net->scheduleResponse(noi2, net->now(), makeResponseStatus(respObj2.obj()));
         net->runReadyNetworkOperations();
@@ -457,7 +457,7 @@ namespace {
         net->blackHole(net->getNextReadyRequest());
 
         // schedule hb reconfig
-        net->runUntil(net->now() + 10*1000); // run until we've sent a heartbeat request
+        net->runUntil(net->now() + Seconds(10)); // run until we've sent a heartbeat request
         const NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
         ReplSetHeartbeatResponse hbResp;
         ReplicaSetConfig config;
diff --git a/src/mongo/db/repl/replication_coordinator_impl_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
index b33b87b1a83..006db55e81b 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
@@ -241,11 +241,11 @@ namespace {
         ASSERT_EQUALS(HostAndPort("node2", 54321), noi->getRequest().target);
         ASSERT_EQUALS("admin", noi->getRequest().dbname);
         ASSERT_EQUALS(hbArgs.toBSON(), noi->getRequest().cmdObj);
-        getNet()->scheduleResponse(noi, startDate + 10, ResponseStatus(ErrorCodes::NoSuchKey,
-                                                                       "No response"));
-        getNet()->runUntil(startDate + 10);
+        getNet()->scheduleResponse(noi, startDate + Milliseconds(10),
+                                   ResponseStatus(ErrorCodes::NoSuchKey, "No response"));
+        getNet()->runUntil(startDate + Milliseconds(10));
         getNet()->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, getNet()->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), getNet()->now());
         prsiThread.join();
         ASSERT_EQUALS(ErrorCodes::NodeNotFound, status);
         ASSERT_EQUALS(MemberState::RS_STARTUP, getReplCoord()->getMemberState().s);
@@ -276,11 +276,11 @@ namespace {
         hbResp.setVersion(0);
         getNet()->scheduleResponse(
                 noi,
-                startDate + 10,
+                startDate + Milliseconds(10),
                 ResponseStatus(RemoteCommandResponse(hbResp.toBSON(), Milliseconds(8))));
-        getNet()->runUntil(startDate + 10);
+        getNet()->runUntil(startDate + Milliseconds(10));
         getNet()->exitNetwork();
-        ASSERT_EQUALS(startDate + 10, getNet()->now());
+        ASSERT_EQUALS(startDate + Milliseconds(10), getNet()->now());
         prsiThread.join();
         ASSERT_OK(status);
         ASSERT_EQUALS(ReplicationCoordinator::modeReplSet, getReplCoord()->getReplicationMode());
@@ -647,7 +647,7 @@ namespace {
         ReplicationAwaiter(ReplicationCoordinatorImpl* replCoord, OperationContext* txn) :
             _replCoord(replCoord), _finished(false),
             _result(ReplicationCoordinator::StatusAndDuration(
-                    Status::OK(), ReplicationCoordinator::Milliseconds(0))) {}
+                    Status::OK(), Milliseconds(0))) {}
 
         void setOpTime(const Timestamp& ot) {
             _optime = ot;
@@ -675,7 +675,7 @@ namespace {
             ASSERT(_finished);
             _finished = false;
             _result = ReplicationCoordinator::StatusAndDuration(
-                    Status::OK(), ReplicationCoordinator::Milliseconds(0));
+                    Status::OK(), Milliseconds(0));
         }
 
     private:
@@ -952,7 +952,7 @@ namespace {
         simulateSuccessfulElection();
 
         enterNetwork();
-        getNet()->runUntil(getNet()->now() + 2000);
+        getNet()->runUntil(getNet()->now() + Seconds(2));
         ASSERT(getNet()->hasReadyRequests());
         NetworkInterfaceMock::NetworkOperationIterator noi = getNet()->getNextReadyRequest();
         RemoteCommandRequest request = noi->getRequest();
@@ -979,7 +979,7 @@ namespace {
         ASSERT_TRUE(getReplCoord()->getMemberState().primary());
         ASSERT_OK(getReplCoord()->stepDown(&txn, false, Milliseconds(0), Milliseconds(1000)));
         enterNetwork(); // So we can safely inspect the topology coordinator
-        ASSERT_EQUALS(Date_t(getNet()->now().millis + 1000), getTopoCoord().getStepDownTime());
+        ASSERT_EQUALS(getNet()->now() + Seconds(1), getTopoCoord().getStepDownTime());
         ASSERT_TRUE(getTopoCoord().getMemberState().secondary());
         exitNetwork();
         ASSERT_TRUE(getReplCoord()->getMemberState().secondary());
@@ -999,7 +999,7 @@ namespace {
         ASSERT_TRUE(getReplCoord()->getMemberState().primary());
         ASSERT_OK(getReplCoord()->stepDown(&txn, true, Milliseconds(0), Milliseconds(1000)));
         getNet()->enterNetwork(); // Must do this before inspecting the topocoord
-        Date_t stepdownUntil = Date_t(getNet()->now().millis + 1000);
+        Date_t stepdownUntil = getNet()->now() + Seconds(1);
         ASSERT_EQUALS(stepdownUntil, getTopoCoord().getStepDownTime());
         ASSERT_TRUE(getTopoCoord().getMemberState().secondary());
         ASSERT_TRUE(getReplCoord()->getMemberState().secondary());
@@ -1103,11 +1103,11 @@ namespace {
         runner.reset();
         getNet()->enterNetwork();
         const Date_t startDate = getNet()->now();
-        while (startDate + 1000 < getNet()->now()) {
+        while (startDate + Milliseconds(1000) < getNet()->now()) {
             while (getNet()->hasReadyRequests()) {
                 getNet()->blackHole(getNet()->getNextReadyRequest());
             }
-            getNet()->runUntil(startDate + 1000);
+            getNet()->runUntil(startDate + Milliseconds(1000));
         }
         getNet()->exitNetwork();
         ASSERT_TRUE(getReplCoord()->getMemberState().primary());
@@ -1140,7 +1140,7 @@ namespace {
 
         // Make a secondary actually catch up
         enterNetwork();
-        getNet()->runUntil(getNet()->now() + 2000);
+        getNet()->runUntil(getNet()->now() + Milliseconds(2000));
         ASSERT(getNet()->hasReadyRequests());
         NetworkInterfaceMock::NetworkOperationIterator noi = getNet()->getNextReadyRequest();
         RemoteCommandRequest request = noi->getRequest();
@@ -1497,7 +1497,7 @@ namespace {
         ASSERT_TRUE(response.isPassive());
         ASSERT_FALSE(response.isHidden());
         ASSERT_TRUE(response.shouldBuildIndexes());
-        ASSERT_EQUALS(0, response.getSlaveDelay().total_seconds());
+        ASSERT_EQUALS(Seconds(0), response.getSlaveDelay());
         ASSERT_EQUALS(h4, response.getMe());
 
         std::vector<HostAndPort> hosts = response.getHosts();
diff --git a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
index 160cb55281d..24c3ee06006 100644
--- a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
+++ b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
@@ -234,7 +234,7 @@ namespace {
         while (replCoord->getMemberState().primary()) {
             log() << "Waiting on network in state " << replCoord->getMemberState();
             getNet()->enterNetwork();
-            net->runUntil(net->now() + 10000);
+            net->runUntil(net->now() + Seconds(10));
             const NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
             const RemoteCommandRequest& request = noi->getRequest();
             log() << request.target.toString() << " processing " << request.cmdObj;
diff --git a/src/mongo/db/repl/replication_executor.cpp b/src/mongo/db/repl/replication_executor.cpp
index be8dbb0ba9f..29d5056e067 100644
--- a/src/mongo/db/repl/replication_executor.cpp
+++ b/src/mongo/db/repl/replication_executor.cpp
@@ -293,8 +293,7 @@ namespace {
             scheduledRequest.expirationDate = kNoExpirationDate;
         }
         else {
-            scheduledRequest.expirationDate =
-                _networkInterface->now() + scheduledRequest.timeout.total_milliseconds();
+            scheduledRequest.expirationDate = _networkInterface->now() + scheduledRequest.timeout;
         }
         boost::lock_guard<boost::mutex> lk(_mutex);
         StatusWith<CallbackHandle> handle = enqueueWork_inlock(
@@ -466,7 +465,7 @@ namespace {
                 return std::make_pair(WorkItem(), CallbackHandle());
             }
             lk.unlock();
-            if (nextWakeupDate == Date_t(~0ULL)) {
+            if (nextWakeupDate == Date_t::max()) {
                 _networkInterface->waitForWork();
             }
             else {
@@ -493,7 +492,7 @@ namespace {
         _readyQueue.splice(_readyQueue.end(), _sleepersQueue, _sleepersQueue.begin(), iter);
         if (iter == _sleepersQueue.end()) {
             // indicate no sleeper to wait for
-            return Date_t(~0ULL);
+            return Date_t::max();
         }
         return iter->readyDate;
     }
diff --git a/src/mongo/db/repl/replication_executor.h b/src/mongo/db/repl/replication_executor.h
index ea19ac411c2..c01bc48e648 100644
--- a/src/mongo/db/repl/replication_executor.h
+++ b/src/mongo/db/repl/replication_executor.h
@@ -28,7 +28,6 @@
 
 #pragma once
 
-#include <boost/date_time/posix_time/posix_time_types.hpp>
 #include <boost/shared_ptr.hpp>
 #include <boost/thread/condition_variable.hpp>
 #include <boost/thread/mutex.hpp>
@@ -110,7 +109,6 @@ namespace repl {
     class ReplicationExecutor {
         MONGO_DISALLOW_COPYING(ReplicationExecutor);
     public:
-        typedef boost::posix_time::milliseconds Milliseconds;
         struct CallbackData;
         class CallbackHandle;
         class EventHandle;
diff --git a/src/mongo/db/repl/replication_executor_test.cpp b/src/mongo/db/repl/replication_executor_test.cpp
index 5b1c62ea13d..a2894d5be15 100644
--- a/src/mongo/db/repl/replication_executor_test.cpp
+++ b/src/mongo/db/repl/replication_executor_test.cpp
@@ -284,22 +284,22 @@ namespace {
         Status status3(ErrorCodes::InternalError, "Not mutated");
         const Date_t now = net->now();
         const ReplicationExecutor::CallbackHandle cb1 =
-            unittest::assertGet(executor.scheduleWorkAt(Date_t(now.millis + 100),
+            unittest::assertGet(executor.scheduleWorkAt(now + Milliseconds(100),
                                                         stdx::bind(setStatus,
                                                                    stdx::placeholders::_1,
                                                                    &status1)));
-        unittest::assertGet(executor.scheduleWorkAt(Date_t(now.millis + 5000),
+        unittest::assertGet(executor.scheduleWorkAt(now + Milliseconds(5000),
                                                     stdx::bind(setStatus,
                                                                stdx::placeholders::_1,
                                                                &status3)));
         const ReplicationExecutor::CallbackHandle cb2 =
-            unittest::assertGet(executor.scheduleWorkAt(Date_t(now.millis + 200),
+            unittest::assertGet(executor.scheduleWorkAt(now + Milliseconds(200),
                                                         stdx::bind(setStatusAndShutdown,
                                                                    stdx::placeholders::_1,
                                                                    &status2)));
         const Date_t startTime = net->now();
-        net->runUntil(startTime + 200 /*ms*/);
-        ASSERT_EQUALS(startTime + 200, net->now());
+        net->runUntil(startTime + Milliseconds(200));
+        ASSERT_EQUALS(startTime + Milliseconds(200), net->now());
         executor.wait(cb1);
         executor.wait(cb2);
         ASSERT_OK(status1);
@@ -457,7 +457,7 @@ namespace {
                 HostAndPort("lazy", 27017),
                 "admin",
                 BSON("sleep" << 1),
-                ReplicationExecutor::Milliseconds(1));
+                Milliseconds(1));
         ReplicationExecutor::CallbackHandle cbHandle = unittest::assertGet(
                 executor.scheduleRemoteCommand(
                         request,
@@ -469,10 +469,10 @@ namespace {
         const Date_t startTime = net->now();
         NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
         net->scheduleResponse(noi,
-                              startTime + 2,
+                              startTime + Milliseconds(2),
                               ResponseStatus(ErrorCodes::ExceededTimeLimit, "I took too long"));
-        net->runUntil(startTime + 2);
-        ASSERT_EQUALS(startTime + 2, net->now());
+        net->runUntil(startTime + Milliseconds(2));
+        ASSERT_EQUALS(startTime + Milliseconds(2), net->now());
         executor.wait(cbHandle);
         ASSERT_EQUALS(ErrorCodes::ExceededTimeLimit, status);
     }
diff --git a/src/mongo/db/repl/replication_info.cpp b/src/mongo/db/repl/replication_info.cpp
index a5303072fbd..fe843605d10 100644
--- a/src/mongo/db/repl/replication_info.cpp
+++ b/src/mongo/db/repl/replication_info.cpp
@@ -126,8 +126,9 @@ namespace repl {
                                                              Query().sort( BSON( "$natural" << -1 ) ) );
                         bb.appendDate( "masterFirst" , first["ts"].timestampTime() );
                         bb.appendDate( "masterLast" , last["ts"].timestampTime() );
-                        double lag = (double) (last["ts"].timestampTime() - s["syncedTo"].timestampTime());
-                        bb.append( "lagSeconds" , lag / 1000 );
+                        const auto lag =
+                            (last["ts"].timestampTime() - s["syncedTo"].timestampTime());
+                        bb.append("lagSeconds", durationCount<Milliseconds>(lag) / 1000.0);
                     }
                     conn.done();
                 }
diff --git a/src/mongo/db/repl/replset_commands.cpp b/src/mongo/db/repl/replset_commands.cpp
index 342ee8e514b..c91cc42ec2d 100644
--- a/src/mongo/db/repl/replset_commands.cpp
+++ b/src/mongo/db/repl/replset_commands.cpp
@@ -534,8 +534,8 @@ namespace {
             status = getGlobalReplicationCoordinator()->stepDown(
                     txn,
                     force,
-                    ReplicationCoordinator::Milliseconds(secondaryCatchUpPeriodSecs * 1000),
-                    ReplicationCoordinator::Milliseconds(stepDownForSecs * 1000));
+                    Seconds(secondaryCatchUpPeriodSecs),
+                    Seconds(stepDownForSecs));
             return appendCommandStatus(result, status);
         }
     } cmdReplSetStepDown;
diff --git a/src/mongo/db/repl/reporter_test.cpp b/src/mongo/db/repl/reporter_test.cpp
index c060f714339..098096461c1 100644
--- a/src/mongo/db/repl/reporter_test.cpp
+++ b/src/mongo/db/repl/reporter_test.cpp
@@ -99,7 +99,7 @@ namespace {
     void ReporterTest::scheduleNetworkResponse(const BSONObj& obj) {
         NetworkInterfaceMock* net = getNet();
         ASSERT_TRUE(net->hasReadyRequests());
-        ReplicationExecutor::Milliseconds millis(0);
+        Milliseconds millis(0);
         RemoteCommandResponse response(obj, millis);
         ReplicationExecutor::ResponseStatus responseStatus(response);
         net->scheduleResponse(net->getNextReadyRequest(), net->now(), responseStatus);
diff --git a/src/mongo/db/repl/rs_initialsync.cpp b/src/mongo/db/repl/rs_initialsync.cpp
index 22817bc7746..71e80ceb6f6 100644
--- a/src/mongo/db/repl/rs_initialsync.cpp
+++ b/src/mongo/db/repl/rs_initialsync.cpp
@@ -354,7 +354,7 @@ namespace {
         truncateAndResetOplog(&txn, replCoord, bgsync);
 
         OplogReader r;
-        Timestamp now(Milliseconds(curTimeMillis64()).total_seconds(), 0);
+        Timestamp now(duration_cast<Seconds>(Milliseconds(curTimeMillis64())), 0);
 
         while (r.getHost().empty()) {
             // We must prime the sync source selector so that it considers all candidates regardless
diff --git a/src/mongo/db/repl/scatter_gather_test.cpp b/src/mongo/db/repl/scatter_gather_test.cpp
index a98c5a1f51f..1fc6765e58e 100644
--- a/src/mongo/db/repl/scatter_gather_test.cpp
+++ b/src/mongo/db/repl/scatter_gather_test.cpp
@@ -186,29 +186,29 @@ namespace {
         net->enterNetwork();
         NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
         net->scheduleResponse(noi,
-                              net->now()+2000,
+                              net->now() + Seconds(2),
                               ResponseStatus(RemoteCommandResponse(
                                     BSON("ok" << 1),
-                                    boost::posix_time::milliseconds(10))));
+                                    Milliseconds(10))));
         ASSERT_FALSE(ranCompletion);
 
         noi = net->getNextReadyRequest();
         net->scheduleResponse(noi,
-                              net->now()+2000,
+                              net->now() + Seconds(2),
                               ResponseStatus(RemoteCommandResponse(
                                     BSON("ok" << 1),
-                                    boost::posix_time::milliseconds(10))));
+                                    Milliseconds(10))));
         ASSERT_FALSE(ranCompletion);
 
         noi = net->getNextReadyRequest();
         net->scheduleResponse(noi,
-                              net->now()+5000,
+                              net->now() + Seconds(5),
                               ResponseStatus(RemoteCommandResponse(
                                     BSON("ok" << 1),
-                                    boost::posix_time::milliseconds(10))));
+                                    Milliseconds(10))));
         ASSERT_FALSE(ranCompletion);
 
-        net->runUntil(net->now()+2000);
+        net->runUntil(net->now() + Seconds(2));
         ASSERT_TRUE(ranCompletion);
 
         delete sga;
@@ -290,32 +290,31 @@ namespace {
         net->enterNetwork();
         NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
         net->scheduleResponse(noi,
-                              net->now()+2000,
+                              net->now() + Seconds(2),
                               ResponseStatus(RemoteCommandResponse(
                                     BSON("ok" << 1),
-                                    boost::posix_time::milliseconds(10))));
+                                    Milliseconds(10))));
         ASSERT_FALSE(ranCompletion);
 
         noi = net->getNextReadyRequest();
         net->scheduleResponse(noi,
-                              net->now()+2000,
+                              net->now() + Seconds(2),
                               ResponseStatus(RemoteCommandResponse(
                                     BSON("ok" << 1),
-                                    boost::posix_time::milliseconds(10))));
+                                    Milliseconds(10))));
         ASSERT_FALSE(ranCompletion);
 
         noi = net->getNextReadyRequest();
         net->scheduleResponse(noi,
-                              net->now()+5000,
+                              net->now() + Seconds(5),
                               ResponseStatus(RemoteCommandResponse(
                                     BSON("ok" << 1),
-                                    boost::posix_time::milliseconds(10))));
+                                    Milliseconds(10))));
         ASSERT_FALSE(ranCompletion);
 
-        net->runUntil(net->now()+2000);
+        net->runUntil(net->now() + Seconds(2));
         ASSERT_TRUE(ranCompletion);
 
-
         net->runReadyNetworkOperations();
         // the third resposne should not be processed, so the count should not increment
         ASSERT_EQUALS(2, sga.getResponseCount());
@@ -400,7 +399,7 @@ namespace {
                               net->now(),
                               ResponseStatus(RemoteCommandResponse(
                                     BSON("ok" << 1),
-                                    boost::posix_time::milliseconds(10))));
+                                    Milliseconds(10))));
         net->runReadyNetworkOperations();
 
         noi = net->getNextReadyRequest();
@@ -412,7 +411,7 @@ namespace {
                               net->now(),
                               ResponseStatus(RemoteCommandResponse(
                                     BSON("ok" << 1),
-                                    boost::posix_time::milliseconds(10))));
+                                    Milliseconds(10))));
         net->runReadyNetworkOperations();
         net->exitNetwork();
 
diff --git a/src/mongo/db/repl/sync_source_feedback.cpp b/src/mongo/db/repl/sync_source_feedback.cpp
index 674555f7c53..6773758ef7c 100644
--- a/src/mongo/db/repl/sync_source_feedback.cpp
+++ b/src/mongo/db/repl/sync_source_feedback.cpp
@@ -127,8 +127,7 @@ namespace repl {
         catch (const DBException& e) {
             log() << "SyncSourceFeedback error sending update: " << e.what() << endl;
             // blacklist sync target for .5 seconds and find a new one
-            replCoord->blacklistSyncSource(_syncTarget,
-                                           Date_t(curTimeMillis64() + 500));
+            replCoord->blacklistSyncSource(_syncTarget, Date_t::now() + Milliseconds(500));
             BackgroundSync::get()->clearSyncTarget();
             _resetConnection();
             return e.toStatus();
@@ -141,8 +140,7 @@ namespace repl {
             // to the syncsource having a newer config
             if (status != ErrorCodes::InvalidReplicaSetConfig || res["cfgver"].eoo() ||
                     res["cfgver"].numberLong() < replCoord->getConfig().getConfigVersion()) {
-                replCoord->blacklistSyncSource(_syncTarget,
-                                               Date_t(curTimeMillis64() + 500));
+                replCoord->blacklistSyncSource(_syncTarget, Date_t::now() + Milliseconds(500));
                 BackgroundSync::get()->clearSyncTarget();
                 _resetConnection();
             }
diff --git a/src/mongo/db/repl/sync_tail.cpp b/src/mongo/db/repl/sync_tail.cpp
index f3d20488f69..4b37ea14c89 100644
--- a/src/mongo/db/repl/sync_tail.cpp
+++ b/src/mongo/db/repl/sync_tail.cpp
@@ -500,7 +500,7 @@ namespace {
                     tryToGoLiveAsASecondary(&txn, replCoord);
                 }
 
-                const int slaveDelaySecs = replCoord->getSlaveDelaySecs().total_seconds();
+                const int slaveDelaySecs = replCoord->getSlaveDelaySecs().count();
                 if (!ops.empty() && slaveDelaySecs > 0) {
                     const BSONObj& lastOp = ops.getDeque().back();
                     const unsigned int opTimestampSecs = lastOp["ts"].timestamp().getSecs();
@@ -620,7 +620,7 @@ namespace {
 
     void SyncTail::handleSlaveDelay(const BSONObj& lastOp) {
         ReplicationCoordinator* replCoord = getGlobalReplicationCoordinator();
-        int slaveDelaySecs = replCoord->getSlaveDelaySecs().total_seconds();
+        int slaveDelaySecs = replCoord->getSlaveDelaySecs().count();
 
         // ignore slaveDelay if the box is still initializing. once
         // it becomes secondary we can worry about it.
@@ -645,7 +645,7 @@ namespace {
                         sleepsecs(6);
 
                         // Handle reconfigs that changed the slave delay
-                        if (replCoord->getSlaveDelaySecs().total_seconds() != slaveDelaySecs)
+                        if (replCoord->getSlaveDelaySecs().count() != slaveDelaySecs)
                             break;
                     }
                 }
diff --git a/src/mongo/db/repl/topology_coordinator_impl.cpp b/src/mongo/db/repl/topology_coordinator_impl.cpp
index 784f682e1ab..30df7dca0f4 100644
--- a/src/mongo/db/repl/topology_coordinator_impl.cpp
+++ b/src/mongo/db/repl/topology_coordinator_impl.cpp
@@ -68,7 +68,7 @@ namespace {
 
     // Interval between the time the last heartbeat from a node was received successfully, or
     // the time when we gave up retrying, and when the next heartbeat should be sent to a target.
-    const Milliseconds kHeartbeatInterval(Seconds(2).total_milliseconds());
+    const auto kHeartbeatInterval = Seconds{2};
 
     // Maximum number of retries for a failed heartbeat.
     const int kMaxHeartbeatRetries = 2;
@@ -103,7 +103,6 @@ namespace {
     PingStats::PingStats() :
         count(0),
         value(std::numeric_limits<unsigned int>::max()),
-        _lastHeartbeatStartDate(0),
         _numFailuresSinceLastStart(std::numeric_limits<int>::max()) {
     }
 
@@ -130,8 +129,6 @@ namespace {
         _maxSyncSourceLagSecs(maxSyncSourceLagSecs),
         _selfIndex(-1),
         _stepDownPending(false),
-        _stepDownUntil(0),
-        _electionSleepUntil(0),
         _maintenanceModeCalls(0),
         _followerMode(MemberState::RS_STARTUP2)
     {
@@ -220,17 +217,17 @@ namespace {
         }
         else {
             // choose a time that will exclude no candidates, since we don't see a primary
-            primaryOpTime = Timestamp(_maxSyncSourceLagSecs.total_seconds(), 0);
+            primaryOpTime = Timestamp(_maxSyncSourceLagSecs, 0);
         }
 
         if (primaryOpTime.getSecs() < 
-            static_cast<unsigned int>(_maxSyncSourceLagSecs.total_seconds())) {
+            static_cast<unsigned int>(_maxSyncSourceLagSecs.count())) {
             // erh - I think this means there was just a new election
             // and we don't yet know the new primary's optime
-            primaryOpTime = Timestamp(_maxSyncSourceLagSecs.total_seconds(), 0);
+            primaryOpTime = Timestamp(_maxSyncSourceLagSecs, 0);
         }
 
-        Timestamp oldestSyncOpTime(primaryOpTime.getSecs() - _maxSyncSourceLagSecs.total_seconds(), 0);
+        Timestamp oldestSyncOpTime(primaryOpTime.getSecs() - _maxSyncSourceLagSecs.count(), 0);
 
         int closestIndex = -1;
 
@@ -481,7 +478,7 @@ namespace {
         else if (args.opTime < _latestKnownOpTime(lastOpApplied)) {
             weAreFresher = true;
         }
-        response->appendDate("opTime", lastOpApplied.asULL());
+        response->appendDate("opTime", Date_t::fromMillisSinceEpoch(lastOpApplied.asLL()));
         response->append("fresher", weAreFresher);
 
         std::string errmsg;
@@ -622,12 +619,12 @@ namespace {
                   << highestPriority->getHostAndPort().toString();
             vote = -10000;
         }
-        else if (_voteLease.when.millis + VoteLease::leaseTime.total_milliseconds() >= now.millis &&
+        else if (_voteLease.when + VoteLease::leaseTime >= now &&
                  _voteLease.whoId != args.whoid) {
             log() << "replSet voting no for "
                   <<  hopeful->getHostAndPort().toString()
                   << "; voted for " << _voteLease.whoHostAndPort.toString() << ' '
-                  << (now.millis - _voteLease.when.millis) / 1000 << " secs ago";
+                  << durationCount<Seconds>(now - _voteLease.when) << " secs ago";
         }
         else {
             _voteLease.when = now;
@@ -704,7 +701,7 @@ namespace {
 
         // Heartbeat status message
         response->setHbMsg(_getHbmsg(now));
-        response->setTime(Seconds(Milliseconds(now.asInt64()).total_seconds()));
+        response->setTime(duration_cast<Seconds>(now - Date_t{}));
         response->setOpTime(lastOpApplied);
 
         if (!_syncSource.empty()) {
@@ -763,7 +760,7 @@ namespace {
                 const HostAndPort& target) {
 
         PingStats& hbStats = _pings[target];
-        Milliseconds alreadyElapsed(now.asInt64() - hbStats.getLastHeartbeatStartDate().asInt64());
+        Milliseconds alreadyElapsed = now - hbStats.getLastHeartbeatStartDate();
         if (!_rsConfig.isInitialized() ||
             (hbStats.getNumFailuresSinceLastStart() > kMaxHeartbeatRetries) ||
             (alreadyElapsed >= _rsConfig.getHeartbeatTimeoutPeriodMillis())) {
@@ -793,10 +790,8 @@ namespace {
         const Milliseconds timeoutPeriod(
                 _rsConfig.isInitialized() ?
                 _rsConfig.getHeartbeatTimeoutPeriodMillis() :
-                Milliseconds(
-                        ReplicaSetConfig::kDefaultHeartbeatTimeoutPeriod.total_milliseconds()));
-        const Milliseconds timeout(
-                timeoutPeriod.total_milliseconds() - alreadyElapsed.total_milliseconds());
+                ReplicaSetConfig::kDefaultHeartbeatTimeoutPeriod);
+        const Milliseconds timeout = timeoutPeriod - alreadyElapsed;
         return std::make_pair(hbArgs, timeout);
     }
 
@@ -809,12 +804,12 @@ namespace {
 
         const MemberState originalState = getMemberState();
         PingStats& hbStats = _pings[target];
-        invariant(hbStats.getLastHeartbeatStartDate() != Date_t(0));
+        invariant(hbStats.getLastHeartbeatStartDate() != Date_t());
         if (!hbResponse.isOK()) {
             hbStats.miss();
         }
         else {
-            hbStats.hit(networkRoundTripTime.total_milliseconds());
+            hbStats.hit(networkRoundTripTime.count());
             // Log diagnostics.
             if (hbResponse.getValue().isStateDisagreement()) {
                 LOG(1) << target <<
@@ -826,7 +821,7 @@ namespace {
                             (hbResponse.getStatus().code() == ErrorCodes::Unauthorized) ||
                             (hbResponse.getStatus().code() == ErrorCodes::AuthenticationFailed);
 
-        Milliseconds alreadyElapsed(now.asInt64() - hbStats.getLastHeartbeatStartDate().asInt64());
+        const Milliseconds alreadyElapsed = now - hbStats.getLastHeartbeatStartDate();
         Date_t nextHeartbeatStartDate;
         if (_rsConfig.isInitialized() &&
             (hbStats.getNumFailuresSinceLastStart() <= kMaxHeartbeatRetries) &&
@@ -836,16 +831,16 @@ namespace {
                 LOG(1) << "Bad heartbeat response from " << target <<
                     "; trying again; Retries left: " <<
                     (kMaxHeartbeatRetries - hbStats.getNumFailuresSinceLastStart()) <<
-                    "; " << alreadyElapsed.total_milliseconds() << "ms have already elapsed";
+                    "; " << alreadyElapsed.count() << "ms have already elapsed";
             }
             if (isUnauthorized) {
-                nextHeartbeatStartDate = now + kHeartbeatInterval.total_milliseconds();
+                nextHeartbeatStartDate = now + kHeartbeatInterval;
             } else {
                 nextHeartbeatStartDate = now;
             }
         }
         else {
-            nextHeartbeatStartDate = now + kHeartbeatInterval.total_milliseconds();
+            nextHeartbeatStartDate = now + kHeartbeatInterval;
         }
 
         if (hbResponse.isOK() && hbResponse.getValue().hasConfig()) {
@@ -992,9 +987,7 @@ namespace {
                               << highestPriorityMember.getPriority() << " and is only "
                               << (latestOpTime.getSecs() - highestPriorityMemberOptime.getSecs())
                               << " seconds behind me";
-                        const Date_t until = now +
-                            VoteLease::leaseTime.total_milliseconds() +
-                            kHeartbeatInterval.total_milliseconds();
+                        const Date_t until = now + VoteLease::leaseTime + kHeartbeatInterval;
                         if (_electionSleepUntil < until) {
                             _electionSleepUntil = until;
                         }
@@ -1332,7 +1325,8 @@ namespace {
             response->append("stateStr", myState.toString());
             response->append("uptime", selfUptime);
             response->append("optime", lastOpApplied);
-            response->appendDate("optimeDate", Date_t(lastOpApplied.getSecs() * 1000ULL));
+            response->appendDate("optimeDate",
+                                 Date_t::fromDurationSinceEpoch(Seconds(lastOpApplied.getSecs())));
             if (_maintenanceModeCalls) {
                 response->append("maintenanceMode", _maintenanceModeCalls);
             }
@@ -1359,7 +1353,8 @@ namespace {
                 bb.append("uptime", selfUptime);
                 if (!_selfConfig().isArbiter()) {
                     bb.append("optime", lastOpApplied);
-                    bb.appendDate("optimeDate", Date_t(lastOpApplied.getSecs() * 1000ULL));
+                    bb.appendDate("optimeDate",
+                                  Date_t::fromDurationSinceEpoch(Seconds(lastOpApplied.getSecs())));
                 }
 
                 if (!_syncSource.empty() && !_iAmPrimary()) {
@@ -1376,7 +1371,8 @@ namespace {
 
                 if (myState.primary()) {
                     bb.append("electionTime", _electionTime);
-                    bb.appendDate("electionDate", Date_t(_electionTime.getSecs() * 1000ULL));
+                    bb.appendDate("electionDate",
+                                  Date_t::fromDurationSinceEpoch(Seconds(_electionTime.getSecs())));
                 }
                 bb.appendIntOrLL("configVersion", _rsConfig.getConfigVersion());
                 bb.append("self", true);
@@ -1401,12 +1397,16 @@ namespace {
                     bb.append("stateStr", it->getState().toString());
                 }
 
-                const unsigned int uptime = static_cast<unsigned int> ((it->getUpSince() ?
-                        (now - it->getUpSince()) / 1000 /* convert millis to secs */ : 0));
+                const unsigned int uptime = static_cast<unsigned int>(
+                        (it->getUpSince() != Date_t()?
+                         durationCount<Seconds>(now - it->getUpSince()) :
+                         0));
                 bb.append("uptime", uptime);
                 if (!itConfig.isArbiter()) {
                     bb.append("optime", it->getOpTime());
-                    bb.appendDate("optimeDate", Date_t(it->getOpTime().getSecs() * 1000ULL));
+                    bb.appendDate(
+                            "optimeDate",
+                            Date_t::fromDurationSinceEpoch(Seconds(it->getOpTime().getSecs())));
                 }
                 bb.appendDate("lastHeartbeat", it->getLastHeartbeat());
                 bb.appendDate("lastHeartbeatRecv", it->getLastHeartbeatRecv());
@@ -1428,7 +1428,8 @@ namespace {
                 if (state == MemberState::RS_PRIMARY) {
                     bb.append("electionTime", it->getElectionTime());
                     bb.appendDate("electionDate",
-                                  Date_t(it->getElectionTime().getSecs() * 1000ULL));
+                                  Date_t::fromDurationSinceEpoch(
+                                          Seconds(it->getElectionTime().getSecs())));
                 }
                 bb.appendIntOrLL("configVersion", it->getConfigVersion());
                 membersOut.push_back(bb.obj());
@@ -1468,7 +1469,7 @@ namespace {
         {
             for (ReplicaSetConfig::MemberIterator it = _rsConfig.membersBegin();
                     it != _rsConfig.membersEnd(); ++it) {
-                if (it->isHidden() || it->getSlaveDelay().total_seconds() > 0) {
+                if (it->isHidden() || it->getSlaveDelay() > Seconds{0}) {
                     continue;
                 }
 
@@ -1496,7 +1497,7 @@ namespace {
         else if (selfConfig.getPriority() == 0) {
             response->setIsPassive(true);
         }
-        if (selfConfig.getSlaveDelay().total_seconds()) {
+        if (selfConfig.getSlaveDelay().count()) {
             response->setSlaveDelay(selfConfig.getSlaveDelay());
         }
         if (selfConfig.isHidden()) {
@@ -1547,7 +1548,7 @@ namespace {
                 response->append("warning", "you really want to freeze for only 1 second?");
 
             if (!_iAmPrimary()) {
-                _stepDownUntil = std::max(_stepDownUntil, Date_t(now + (secs * 1000)));
+                _stepDownUntil = std::max(_stepDownUntil, now + Seconds(secs));
                 log() << "'freezing' for " << secs << " seconds";
             }
             else {
@@ -1674,7 +1675,7 @@ namespace {
     }
     std::string TopologyCoordinatorImpl::_getHbmsg(Date_t now) const {
         // ignore messages over 2 minutes old
-        if ((now - _hbmsgTime) > 120) {
+        if ((now - _hbmsgTime) > Seconds{120}) {
             return "";
         }
         return _hbmsg;
@@ -1742,7 +1743,7 @@ namespace {
         }
         if (_voteLease.whoId != -1 &&
                 _voteLease.whoId !=_rsConfig.getMemberAt(_selfIndex).getId() &&
-                _voteLease.when.millis + VoteLease::leaseTime.total_milliseconds() >= now.millis) {
+                _voteLease.when + VoteLease::leaseTime >= now) {
             result |= VotedTooRecently;
         }
 
@@ -1879,11 +1880,11 @@ namespace {
             return false;
         }
         int selfId = _selfConfig().getId();
-        if ((_voteLease.when + VoteLease::leaseTime.total_milliseconds() >= now) 
+        if ((_voteLease.when + VoteLease::leaseTime >= now) 
             && (_voteLease.whoId != selfId)) {
             log() << "not voting yea for " << selfId <<
                 " voted for " << _voteLease.whoHostAndPort.toString() << ' ' << 
-                (now - _voteLease.when) / 1000 << " secs ago";
+                durationCount<Seconds>(now - _voteLease.when) << " secs ago";
             return false;
         }
         _voteLease.when = now;
@@ -1936,7 +1937,7 @@ namespace {
         // Clear voteLease time, if we voted for ourselves in this election.
         // This will allow us to vote for others.
         if (_voteLease.whoId == _selfConfig().getId()) {
-            _voteLease.when = 0;
+            _voteLease.when = Date_t();
         }
     }
 
@@ -2061,7 +2062,7 @@ namespace {
             return false;
         }
         unsigned int currentSecs = currentOpTime.getSecs();
-        unsigned int goalSecs = currentSecs + _maxSyncSourceLagSecs.total_seconds();
+        unsigned int goalSecs = currentSecs + _maxSyncSourceLagSecs.count();
 
         for (std::vector<MemberHeartbeatData>::const_iterator it = _hbdata.begin();
              it != _hbdata.end();
@@ -2075,7 +2076,7 @@ namespace {
                 goalSecs < it->getOpTime().getSecs()) {
                 log() << "changing sync target because current sync target's most recent OpTime is "
                       << currentOpTime.toStringLong() << " which is more than "
-                      << _maxSyncSourceLagSecs.total_seconds() << " seconds behind member " 
+                      << _maxSyncSourceLagSecs.count() << " seconds behind member " 
                       <<  candidateConfig.getHostAndPort().toString()
                       << " whose most recent OpTime is " << it->getOpTime().toStringLong();
                 invariant(itIndex != _selfIndex);
diff --git a/src/mongo/db/repl/topology_coordinator_impl.h b/src/mongo/db/repl/topology_coordinator_impl.h
index 39d186c7308..0bb373cad31 100644
--- a/src/mongo/db/repl/topology_coordinator_impl.h
+++ b/src/mongo/db/repl/topology_coordinator_impl.h
@@ -403,9 +403,8 @@ namespace repl {
 
             static const Seconds leaseTime;
 
-            VoteLease() : when(0), whoId(-1) { }
             Date_t when;
-            int whoId;
+            int whoId = -1;
             HostAndPort whoHostAndPort;
         } _voteLease;
 
diff --git a/src/mongo/db/repl/topology_coordinator_impl_test.cpp b/src/mongo/db/repl/topology_coordinator_impl_test.cpp
index 1e12a7ac2cf..50f462900d7 100644
--- a/src/mongo/db/repl/topology_coordinator_impl_test.cpp
+++ b/src/mongo/db/repl/topology_coordinator_impl_test.cpp
@@ -115,7 +115,7 @@ namespace {
             else {
                 invariant(now > _now);
                 getTopoCoord().updateConfig(config, selfIndex, now, lastOp);
-                _now = now + 1;
+                _now = now + Milliseconds(1);
             }
         }
 
@@ -772,7 +772,7 @@ namespace {
         Date_t startupTime(100);
         Date_t heartbeatTime = 5000;
         Seconds uptimeSecs(10);
-        Date_t curTime = heartbeatTime + uptimeSecs.total_milliseconds();
+        Date_t curTime = heartbeatTime + uptimeSecs;
         Timestamp electionTime(1, 2);
         Timestamp oplogProgress(3, 4);
         std::string setName = "mySet";
@@ -784,13 +784,13 @@ namespace {
                                                   BSON("_id" << 2 << "host" << "test2:1234") <<
                                                   BSON("_id" << 3 << "host" << "test3:1234"))),
                      3,
-                     startupTime + 1);
+                     startupTime + Milliseconds(1));
 
         // Now that the replica set is setup, put the members into the states we want them in.
         HostAndPort member = HostAndPort("test0:1234");
         StatusWith<ReplSetHeartbeatResponse> hbResponse =
                 StatusWith<ReplSetHeartbeatResponse>(Status(ErrorCodes::HostUnreachable, ""));
-        getTopoCoord().prepareHeartbeatRequest(startupTime + 2, setName, member);
+        getTopoCoord().prepareHeartbeatRequest(startupTime + Milliseconds(2), setName, member);
         getTopoCoord().processHeartbeatResponse(heartbeatTime,
                                                 Milliseconds(0),
                                                 member,
@@ -805,7 +805,7 @@ namespace {
         hb.setHbMsg("READY");
         hb.setOpTime(oplogProgress);
         hbResponse = StatusWith<ReplSetHeartbeatResponse>(hb);
-        getTopoCoord().prepareHeartbeatRequest(startupTime + 2,
+        getTopoCoord().prepareHeartbeatRequest(startupTime + Milliseconds(2),
                                                setName,
                                                member);
         getTopoCoord().processHeartbeatResponse(heartbeatTime,
@@ -820,7 +820,7 @@ namespace {
         Status resultStatus(ErrorCodes::InternalError, "prepareStatusResponse didn't set result");
         getTopoCoord().prepareStatusResponse(cbData(),
                                              curTime,
-                                             uptimeSecs.total_seconds(),
+                                             uptimeSecs.count(),
                                              oplogProgress,
                                              &statusBuilder,
                                              &resultStatus);
@@ -845,8 +845,8 @@ namespace {
         ASSERT_EQUALS(0, member0Status["uptime"].numberInt());
         ASSERT_EQUALS(Timestamp(), Timestamp(member0Status["optime"].timestampValue()));
         ASSERT_TRUE(member0Status.hasField("optimeDate"));
-        ASSERT_EQUALS(Date_t(Timestamp().getSecs() * 1000ULL),
-                      member0Status["optimeDate"].Date().millis);
+        ASSERT_EQUALS(Date_t::fromMillisSinceEpoch(Timestamp().getSecs() * 1000ULL),
+                      member0Status["optimeDate"].Date());
         ASSERT_EQUALS(heartbeatTime, member0Status["lastHeartbeat"].date());
         ASSERT_EQUALS(Date_t(), member0Status["lastHeartbeatRecv"].date());
 
@@ -857,11 +857,11 @@ namespace {
         ASSERT_EQUALS(MemberState::RS_SECONDARY, member1Status["state"].numberInt());
         ASSERT_EQUALS(MemberState(MemberState::RS_SECONDARY).toString(),
                       member1Status["stateStr"].String());
-        ASSERT_EQUALS(uptimeSecs.total_seconds(), member1Status["uptime"].numberInt());
+        ASSERT_EQUALS(uptimeSecs.count(), member1Status["uptime"].numberInt());
         ASSERT_EQUALS(oplogProgress, Timestamp(member1Status["optime"].timestampValue()));
         ASSERT_TRUE(member1Status.hasField("optimeDate"));
-        ASSERT_EQUALS(Date_t(oplogProgress.getSecs() * 1000ULL),
-                      member1Status["optimeDate"].Date().millis);
+        ASSERT_EQUALS(Date_t::fromMillisSinceEpoch(oplogProgress.getSecs() * 1000ULL),
+                      member1Status["optimeDate"].Date());
         ASSERT_EQUALS(heartbeatTime, member1Status["lastHeartbeat"].date());
         ASSERT_EQUALS(Date_t(), member1Status["lastHeartbeatRecv"].date());
         ASSERT_EQUALS("READY", member1Status["lastHeartbeatMessage"].str());
@@ -889,11 +889,11 @@ namespace {
         ASSERT_EQUALS(MemberState::RS_PRIMARY, selfStatus["state"].numberInt());
         ASSERT_EQUALS(MemberState(MemberState::RS_PRIMARY).toString(),
                       selfStatus["stateStr"].str());
-        ASSERT_EQUALS(uptimeSecs.total_seconds(), selfStatus["uptime"].numberInt());
+        ASSERT_EQUALS(uptimeSecs.count(), selfStatus["uptime"].numberInt());
         ASSERT_EQUALS(oplogProgress, Timestamp(selfStatus["optime"].timestampValue()));
         ASSERT_TRUE(selfStatus.hasField("optimeDate"));
-        ASSERT_EQUALS(Date_t(oplogProgress.getSecs() * 1000ULL),
-                      selfStatus["optimeDate"].Date().millis);
+        ASSERT_EQUALS(Date_t::fromMillisSinceEpoch(oplogProgress.getSecs() * 1000ULL),
+                      selfStatus["optimeDate"].Date());
 
         // TODO(spencer): Test electionTime and pingMs are set properly
     }
@@ -904,7 +904,7 @@ namespace {
         Date_t startupTime(100);
         Date_t heartbeatTime = 5000;
         Seconds uptimeSecs(10);
-        Date_t curTime = heartbeatTime + uptimeSecs.total_milliseconds();
+        Date_t curTime = heartbeatTime + uptimeSecs;
         Timestamp oplogProgress(3, 4);
         std::string setName = "mySet";
 
@@ -914,13 +914,13 @@ namespace {
                                                   BSON("_id" << 1 << "host" << "test1:1234") <<
                                                   BSON("_id" << 2 << "host" << "test2:1234"))),
                      -1,  // This one is not part of the replica set.
-                     startupTime + 1);
+                     startupTime + Milliseconds(1));
 
         BSONObjBuilder statusBuilder;
         Status resultStatus(ErrorCodes::InternalError, "prepareStatusResponse didn't set result");
         getTopoCoord().prepareStatusResponse(cbData(),
                                              curTime,
-                                             uptimeSecs.total_seconds(),
+                                             uptimeSecs.count(),
                                              oplogProgress,
                                              &statusBuilder,
                                              &resultStatus);
@@ -1211,12 +1211,12 @@ namespace {
                                                        "rs0",
                                                        _target);
             // 5 seconds to successfully complete the heartbeat before the timeout expires.
-            ASSERT_EQUALS(5000, request.second.total_milliseconds());
+            ASSERT_EQUALS(5000, request.second.count());
 
             // Initial heartbeat request fails at t + 4000ms
             HeartbeatResponseAction action =
                 getTopoCoord().processHeartbeatResponse(
-                        _firstRequestDate + 4000, // 4 seconds elapsed, retry allowed.
+                        _firstRequestDate + Seconds(4), // 4 seconds elapsed, retry allowed.
                         Milliseconds(3990), // Spent 3.99 of the 4 seconds in the network.
                         _target,
                         StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::ExceededTimeLimit,
@@ -1226,16 +1226,17 @@ namespace {
             ASSERT_EQUALS(HeartbeatResponseAction::NoAction, action.getAction());
             ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
             // Because the heartbeat failed without timing out, we expect to retry immediately.
-            ASSERT_EQUALS(Date_t(_firstRequestDate + 4000), action.getNextHeartbeatStartDate());
+            ASSERT_EQUALS(Date_t(_firstRequestDate + Seconds(4)),
+                          action.getNextHeartbeatStartDate());
 
             // First heartbeat retry prepared, at t + 4000ms.
             request =
                 getTopoCoord().prepareHeartbeatRequest(
-                        _firstRequestDate + 4000,
+                        _firstRequestDate + Milliseconds(4000),
                         "rs0",
                         _target);
             // One second left to complete the heartbeat.
-            ASSERT_EQUALS(1000, request.second.total_milliseconds());
+            ASSERT_EQUALS(1000, request.second.count());
         }
         
         Date_t firstRequestDate() {
@@ -1259,7 +1260,8 @@ namespace {
             // First retry fails at t + 4500ms
             HeartbeatResponseAction action =
                 getTopoCoord().processHeartbeatResponse(
-                        firstRequestDate() + 4500, // 4.5 of the 5 seconds elapsed; could retry.
+                        firstRequestDate() + Milliseconds(4500), // 4.5 of the 5 seconds elapsed;
+                                                                 // could retry.
                         Milliseconds(400), // Spent 0.4 of the 0.5 seconds in the network.
                         target(),
                         StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::NodeNotFound, "Bad DNS?"),
@@ -1267,16 +1269,17 @@ namespace {
             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.
-            ASSERT_EQUALS(Date_t(firstRequestDate() + 4500), action.getNextHeartbeatStartDate());
+            ASSERT_EQUALS(firstRequestDate() + Milliseconds(4500),
+                          action.getNextHeartbeatStartDate());
 
             // Second retry prepared at t + 4500ms.
             std::pair<ReplSetHeartbeatArgs, Milliseconds> request =
                 getTopoCoord().prepareHeartbeatRequest(
-                        firstRequestDate() + 4500,
+                        firstRequestDate() + Milliseconds(4500),
                         "rs0",
                         target());
             // 500ms left to complete the heartbeat.
-            ASSERT_EQUALS(500, request.second.total_milliseconds());
+            ASSERT_EQUALS(500, request.second.count());
         }
     };
 
@@ -1436,14 +1439,14 @@ namespace {
         reconfigResponse.setConfig(newConfig);
         HeartbeatResponseAction action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 4500, // Time is left.
+                    firstRequestDate() + Milliseconds(4500), // Time is left.
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(reconfigResponse),
                     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());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(6500), action.getNextHeartbeatStartDate());
     }
 
     TEST_F(HeartbeatResponseTestOneRetry, DecideToStepDownRemotePrimary) {
@@ -1464,14 +1467,14 @@ namespace {
         electedMoreRecentlyResponse.setVersion(5);
         HeartbeatResponseAction action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 4500, // Time is left.
+                    firstRequestDate() + Milliseconds(4500), // Time is left.
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(electedMoreRecentlyResponse),
                     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());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(6500), action.getNextHeartbeatStartDate());
     }
 
     TEST_F(HeartbeatResponseTestOneRetry, DecideToStepDownSelf) {
@@ -1496,14 +1499,14 @@ namespace {
         electedMoreRecentlyResponse.setVersion(5);
         action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 4500, // Time is left.
+                    firstRequestDate() + Milliseconds(4500), // Time is left.
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(electedMoreRecentlyResponse),
                     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());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(6500), action.getNextHeartbeatStartDate());
         // Doesn't actually do the stepdown until stepDownIfPending is called
         ASSERT_TRUE(TopologyCoordinator::Role::leader == getTopoCoord().getRole());
         ASSERT_EQUALS(0, getCurrentPrimaryIndex());
@@ -1539,14 +1542,14 @@ namespace {
         startElectionResponse.setVersion(5);
         action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 4500, // Time is left.
+                    firstRequestDate() + Milliseconds(4500), // Time is left.
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(startElectionResponse),
                     election);
         ASSERT_EQUALS(HeartbeatResponseAction::StartElection, action.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
-        ASSERT_EQUALS(Date_t(firstRequestDate() + 6500), action.getNextHeartbeatStartDate());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(6500), action.getNextHeartbeatStartDate());
     }
 
     TEST_F(HeartbeatResponseTestTwoRetries, HeartbeatRetriesAtMostTwice) {
@@ -1562,7 +1565,8 @@ namespace {
         // Second retry fails at t + 4800ms
         HeartbeatResponseAction action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 4800, // 4.8 of the 5 seconds elapsed; could still retry.
+                    firstRequestDate() + Milliseconds(4800), // 4.8 of the 5 seconds elapsed;
+                                                             // could still retry.
                     Milliseconds(100), // Spent 0.1 of the 0.3 seconds in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::NodeNotFound, "Bad DNS?"),
@@ -1571,7 +1575,7 @@ namespace {
         ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
         // Because this is the second retry, rather than retry again, we expect to wait for the
         // heartbeat interval of 2 seconds to elapse.
-        ASSERT_EQUALS(Date_t(firstRequestDate() + 6800), action.getNextHeartbeatStartDate());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(6800), action.getNextHeartbeatStartDate());
     }
 
     TEST_F(HeartbeatResponseTestTwoRetries, DecideToStepDownRemotePrimary) {
@@ -1592,14 +1596,14 @@ namespace {
         electedMoreRecentlyResponse.setVersion(5);
         HeartbeatResponseAction action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 5000, // Time is left.
+                    firstRequestDate() + Milliseconds(5000), // Time is left.
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(electedMoreRecentlyResponse),
                     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());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(7000), action.getNextHeartbeatStartDate());
     }
 
     TEST_F(HeartbeatResponseTestTwoRetries, DecideToStepDownSelf) {
@@ -1624,14 +1628,14 @@ namespace {
         electedMoreRecentlyResponse.setVersion(5);
         action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 5000, // Time is left.
+                    firstRequestDate() + Milliseconds(5000), // Time is left.
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(electedMoreRecentlyResponse),
                     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());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(7000), action.getNextHeartbeatStartDate());
         // Doesn't actually do the stepdown until stepDownIfPending is called
         ASSERT_TRUE(TopologyCoordinator::Role::leader == getTopoCoord().getRole());
         ASSERT_EQUALS(0, getCurrentPrimaryIndex());
@@ -1667,14 +1671,14 @@ namespace {
         startElectionResponse.setVersion(5);
         action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 5000, // Time is left.
+                    firstRequestDate() + Milliseconds(5000), // Time is left.
                     Milliseconds(400), // Spent 0.4 of the 0.5 second in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(startElectionResponse),
                     election);
         ASSERT_EQUALS(HeartbeatResponseAction::StartElection, action.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::candidate == getTopoCoord().getRole());
-        ASSERT_EQUALS(Date_t(firstRequestDate() + 7000), action.getNextHeartbeatStartDate());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(7000), action.getNextHeartbeatStartDate());
     }
 
     TEST_F(HeartbeatResponseTest, HeartbeatTimeoutSuppressesFirstRetry) {
@@ -1690,12 +1694,13 @@ namespace {
                                                    "rs0",
                                                    target);
         // 5 seconds to successfully complete the heartbeat before the timeout expires.
-        ASSERT_EQUALS(5000, request.second.total_milliseconds());
+        ASSERT_EQUALS(5000, request.second.count());
 
         // Initial heartbeat request fails at t + 5000ms
         HeartbeatResponseAction action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate + 5000, // Entire heartbeat period elapsed; no retry allowed.
+                    firstRequestDate + Milliseconds(5000), // Entire heartbeat period elapsed;
+                                                           // no retry allowed.
                     Milliseconds(4990), // Spent 4.99 of the 4 seconds in the network.
                     target,
                     StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::ExceededTimeLimit,
@@ -1705,7 +1710,7 @@ namespace {
         ASSERT_EQUALS(HeartbeatResponseAction::NoAction, action.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
         // Because the heartbeat timed out, we'll retry in 2 seconds.
-        ASSERT_EQUALS(Date_t(firstRequestDate + 7000), action.getNextHeartbeatStartDate());
+        ASSERT_EQUALS(firstRequestDate + Milliseconds(7000), action.getNextHeartbeatStartDate());
     }
 
     TEST_F(HeartbeatResponseTestOneRetry, HeartbeatTimeoutSuppressesSecondRetry) {
@@ -1713,7 +1718,8 @@ namespace {
         // the heartbeat timeout period expired before the first retry completed.
         HeartbeatResponseAction action =
             getTopoCoord().processHeartbeatResponse(
-                    firstRequestDate() + 5010, // Entire heartbeat period elapsed; no retry allowed.
+                    firstRequestDate() + Milliseconds(5010), // Entire heartbeat period elapsed;
+                                                             // no retry allowed.
                     Milliseconds(1000), // Spent 1 of the 1.01 seconds in the network.
                     target(),
                     StatusWith<ReplSetHeartbeatResponse>(ErrorCodes::ExceededTimeLimit,
@@ -1723,7 +1729,7 @@ namespace {
         ASSERT_EQUALS(HeartbeatResponseAction::NoAction, action.getAction());
         ASSERT_TRUE(TopologyCoordinator::Role::follower == getTopoCoord().getRole());
         // Because the heartbeat timed out, we'll retry in 2 seconds.
-        ASSERT_EQUALS(Date_t(firstRequestDate() + 7010), action.getNextHeartbeatStartDate());
+        ASSERT_EQUALS(firstRequestDate() + Milliseconds(7010), action.getNextHeartbeatStartDate());
     }
 
     TEST_F(HeartbeatResponseTest, UpdateHeartbeatDataNewPrimary) {
@@ -3219,7 +3225,7 @@ namespace {
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
         ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
-        ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
+        ASSERT_EQUALS(0, response.getTime().count());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
         ASSERT_EQUALS(1, response.getVersion());
@@ -3242,7 +3248,7 @@ namespace {
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
         ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
-        ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
+        ASSERT_EQUALS(0, response.getTime().count());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
         ASSERT_EQUALS(1, response.getVersion());
@@ -3266,7 +3272,7 @@ namespace {
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
         ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
-        ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
+        ASSERT_EQUALS(0, response.getTime().count());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
         ASSERT_EQUALS(1, response.getVersion());
@@ -3290,7 +3296,7 @@ namespace {
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
         ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
-        ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
+        ASSERT_EQUALS(0, response.getTime().count());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
         ASSERT_EQUALS(1, response.getVersion());
@@ -3313,7 +3319,7 @@ namespace {
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
         ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
-        ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
+        ASSERT_EQUALS(0, response.getTime().count());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
         ASSERT_EQUALS(1, response.getVersion());
@@ -3339,7 +3345,7 @@ namespace {
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
         ASSERT_EQUALS(Timestamp(100,0), response.getOpTime());
-        ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
+        ASSERT_EQUALS(0, response.getTime().count());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
         ASSERT_EQUALS(1, response.getVersion());
@@ -3365,7 +3371,7 @@ namespace {
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_STARTUP, response.getState().s);
         ASSERT_EQUALS(Timestamp(0,0), response.getOpTime());
-        ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
+        ASSERT_EQUALS(0, response.getTime().count());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("", response.getReplicaSetName());
         ASSERT_EQUALS(-2, response.getVersion());
@@ -3392,7 +3398,7 @@ namespace {
         ASSERT_EQUALS(MemberState::RS_PRIMARY, response.getState().s);
         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(0, response.getTime().count());
         ASSERT_EQUALS("", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
         ASSERT_EQUALS(1, response.getVersion());
@@ -3422,7 +3428,7 @@ namespace {
         ASSERT_TRUE(response.isReplSet());
         ASSERT_EQUALS(MemberState::RS_SECONDARY, response.getState().s);
         ASSERT_EQUALS(Timestamp(100,0), response.getOpTime());
-        ASSERT_EQUALS(Seconds(0).total_milliseconds(), response.getTime().total_milliseconds());
+        ASSERT_EQUALS(0, response.getTime().count());
         // changed to a syncing message because our sync source changed recently
         ASSERT_EQUALS("syncing from: h2:27017", response.getHbMsg());
         ASSERT_EQUALS("rs0", response.getReplicaSetName());
@@ -3848,17 +3854,17 @@ namespace {
                                         fresherLastOpTimeApplied,
                                         lastOpTimeApplied);
         ASSERT_NO_ACTION(nextAction.getAction());
-        getTopoCoord().blacklistSyncSource(HostAndPort("host3"), now() + 100);
+        getTopoCoord().blacklistSyncSource(HostAndPort("host3"), now() + Milliseconds(100));
 
         // set up complete, time for actual check
         ASSERT_FALSE(getTopoCoord().shouldChangeSyncSource(HostAndPort("host2"), now()));
 
         // unblacklist with too early a time (node should remained blacklisted)
-        getTopoCoord().unblacklistSyncSource(HostAndPort("host3"), now() + 90);
+        getTopoCoord().unblacklistSyncSource(HostAndPort("host3"), now() + Milliseconds(90));
         ASSERT_FALSE(getTopoCoord().shouldChangeSyncSource(HostAndPort("host2"), now()));
 
         // unblacklist and it should succeed
-        getTopoCoord().unblacklistSyncSource(HostAndPort("host3"), now() + 100);
+        getTopoCoord().unblacklistSyncSource(HostAndPort("host3"), now() + Milliseconds(100));
         startCapturingLogMessages();
         ASSERT_TRUE(getTopoCoord().shouldChangeSyncSource(HostAndPort("host2"), now()));
         stopCapturingLogMessages();
diff --git a/src/mongo/db/stats/range_deleter_server_status.cpp b/src/mongo/db/stats/range_deleter_server_status.cpp
index 408f7049920..e625e16f01b 100644
--- a/src/mongo/db/stats/range_deleter_server_status.cpp
+++ b/src/mongo/db/stats/range_deleter_server_status.cpp
@@ -74,16 +74,16 @@ namespace mongo {
                 BSONObjBuilder entryBuilder;
                 entryBuilder.append("deletedDocs", (*it)->deletedDocCount);
 
-                if ((*it)->queueEndTS.millis > 0) {
+                if ((*it)->queueEndTS > Date_t()) {
                     entryBuilder.append("queueStart", (*it)->queueStartTS);
                     entryBuilder.append("queueEnd", (*it)->queueEndTS);
                 }
 
-                if ((*it)->deleteEndTS.millis > 0) {
+                if ((*it)->deleteEndTS > Date_t()) {
                     entryBuilder.append("deleteStart", (*it)->deleteStartTS);
                     entryBuilder.append("deleteEnd", (*it)->deleteEndTS);
 
-                    if ((*it)->waitForReplEndTS.millis > 0) {
+                    if ((*it)->waitForReplEndTS > Date_t()) {
                         entryBuilder.append("waitForReplStart", (*it)->waitForReplStartTS);
                         entryBuilder.append("waitForReplEnd", (*it)->waitForReplEndTS);
                     }
diff --git a/src/mongo/db/storage/key_string.cpp b/src/mongo/db/storage/key_string.cpp
index 0df4a8d8096..c77e5fc2e72 100644
--- a/src/mongo/db/storage/key_string.cpp
+++ b/src/mongo/db/storage/key_string.cpp
@@ -755,8 +755,8 @@ namespace mongo {
             case CType::kBoolFalse: *stream << false; break;
 
             case CType::kDate:
-                *stream << Date_t(endian::bigToNative(readType<uint64_t>(reader,
-                                                                         inverted)) ^ (1LL << 63));
+                *stream << Date_t::fromMillisSinceEpoch(
+                        endian::bigToNative(readType<uint64_t>(reader, inverted)) ^ (1LL << 63));
                 break;
 
             case CType::kTimestamp:
diff --git a/src/mongo/db/storage/mmap_v1/data_file_sync.cpp b/src/mongo/db/storage/mmap_v1/data_file_sync.cpp
index cf1d1abca88..e8b9d6d5bd4 100644
--- a/src/mongo/db/storage/mmap_v1/data_file_sync.cpp
+++ b/src/mongo/db/storage/mmap_v1/data_file_sync.cpp
@@ -86,7 +86,7 @@ namespace mongo {
             Date_t start = jsTime();
             StorageEngine* storageEngine = getGlobalServiceContext()->getGlobalStorageEngine();
             int numFiles = storageEngine->flushAllFiles( true );
-            time_flushing = (int) (jsTime() - start);
+            time_flushing = (jsTime() - start).count();
 
             _flushed(time_flushing);
 
diff --git a/src/mongo/db/storage/mmap_v1/dur.cpp b/src/mongo/db/storage/mmap_v1/dur.cpp
index 3a1498093bc..b12098199f1 100644
--- a/src/mongo/db/storage/mmap_v1/dur.cpp
+++ b/src/mongo/db/storage/mmap_v1/dur.cpp
@@ -701,7 +701,8 @@ namespace {
                 boost::unique_lock<boost::mutex> lock(flushMutex);
 
                 for (unsigned i = 0; i <= 2; i++) {
-                    if (flushRequested.timed_wait(lock, Milliseconds(oneThird))) {
+                    if (boost::cv_status::no_timeout == flushRequested.wait_for(
+                                lock, Milliseconds(oneThird))) {
                         // Someone forced a flush
                         break;
                     }
diff --git a/src/mongo/db/ttl.cpp b/src/mongo/db/ttl.cpp
index 43845ffaa34..facbb58082c 100644
--- a/src/mongo/db/ttl.cpp
+++ b/src/mongo/db/ttl.cpp
@@ -231,7 +231,7 @@ namespace mongo {
 
             // Read the current time outside of the while loop, so that we don't expand our index
             // bounds after every WriteConflictException.
-            unsigned long long now = curTimeMillis64();
+            const Date_t now = Date_t::now();
 
             long long numDeleted = 0;
             int attempt = 1;
@@ -284,10 +284,11 @@ namespace mongo {
                     return true;
                 }
 
-                const Date_t kDawnOfTime(std::numeric_limits<long long>::min());
+                const Date_t kDawnOfTime =
+                    Date_t::fromMillisSinceEpoch(std::numeric_limits<long long>::min());
                 const BSONObj startKey = BSON("" << kDawnOfTime);
                 const BSONObj endKey =
-                    BSON("" << Date_t(now - (1000 * secondsExpireElt.numberLong())));
+                    BSON("" << now - Seconds(secondsExpireElt.numberLong()));
                 const bool endKeyInclusive = true;
                 // The canonical check as to whether a key pattern element is "ascending" or
                 // "descending" is (elt.number() >= 0).  This is defined by the Ordering class.
diff --git a/src/mongo/db/write_concern.cpp b/src/mongo/db/write_concern.cpp
index 7bb8edd0fa2..dd591ae4975 100644
--- a/src/mongo/db/write_concern.cpp
+++ b/src/mongo/db/write_concern.cpp
@@ -269,8 +269,8 @@ namespace mongo {
         }
         // Add stats
         result->writtenTo = repl::getGlobalReplicationCoordinator()->getHostsWrittenTo(replOpTime);
-        gleWtimeStats.recordMillis(replStatus.duration.total_milliseconds());
-        result->wTime = replStatus.duration.total_milliseconds();
+        gleWtimeStats.recordMillis(replStatus.duration.count());
+        result->wTime = replStatus.duration.count();
 
         return replStatus.status;
     }
diff --git a/src/mongo/dbtests/config_upgrade_tests.cpp b/src/mongo/dbtests/config_upgrade_tests.cpp
index e76760d283f..41ae04a0f80 100644
--- a/src/mongo/dbtests/config_upgrade_tests.cpp
+++ b/src/mongo/dbtests/config_upgrade_tests.cpp
@@ -138,7 +138,7 @@ namespace mongo {
                 ping.setConfigVersion(CURRENT_CONFIG_VERSION);
 
                 if (i % 2 == 0) {
-                    ping.setPing(ping.getPing() - 10 * 60 * 1000);
+                    ping.setPing(ping.getPing() - Minutes(10));
                 }
 
                 client.insert(MongosType::ConfigNS, ping.toBSON());
diff --git a/src/mongo/dbtests/jsobjtests.cpp b/src/mongo/dbtests/jsobjtests.cpp
index 62a69fc6ded..f823e5301ee 100644
--- a/src/mongo/dbtests/jsobjtests.cpp
+++ b/src/mongo/dbtests/jsobjtests.cpp
@@ -1311,7 +1311,8 @@ namespace JsobjTests {
                 const Date_t base( ::time( 0 ) );
                 oid.init( base );
 
-                ASSERT_EQUALS( base.millis / 1000, oid.asDateT().millis / 1000 );
+                ASSERT_EQUALS(base.toMillisSinceEpoch() / 1000,
+                              oid.asDateT().toMillisSinceEpoch() / 1000);
                 ASSERT_EQUALS( base.toTimeT(), oid.asTimeT() );
             }
         };
diff --git a/src/mongo/dbtests/mock/mock_replica_set.cpp b/src/mongo/dbtests/mock/mock_replica_set.cpp
index ea1ebde067a..16d6adbf2d1 100644
--- a/src/mongo/dbtests/mock/mock_replica_set.cpp
+++ b/src/mongo/dbtests/mock/mock_replica_set.cpp
@@ -219,8 +219,8 @@ namespace mongo {
                     builder.append("passive", true);
                 }
 
-                if (member->getSlaveDelay().total_seconds()) {
-                    builder.append("slaveDelay", member->getSlaveDelay().total_seconds());
+                if (member->getSlaveDelay().count()) {
+                    builder.appendIntOrLL("slaveDelay", member->getSlaveDelay().count());
                 }
 
                 if (member->isHidden()) {
diff --git a/src/mongo/dbtests/querytests.cpp b/src/mongo/dbtests/querytests.cpp
index 5aac0a989e5..b0df01de4ed 100644
--- a/src/mongo/dbtests/querytests.cpp
+++ b/src/mongo/dbtests/querytests.cpp
@@ -675,7 +675,7 @@ namespace QueryTests {
             
             ClientCursorPin clientCursor( ctx.db()->getCollection( ns )->getCursorManager(),
                                           cursorId );
-            ASSERT_EQUALS( three.millis, clientCursor.c()->getSlaveReadTill().asULL() );
+            ASSERT_EQUALS( three.asULL(), clientCursor.c()->getSlaveReadTill().asULL() );
         }
     };
 
diff --git a/src/mongo/logger/logstream_builder.cpp b/src/mongo/logger/logstream_builder.cpp
index 1ed0e701c45..1adef55dd6d 100644
--- a/src/mongo/logger/logstream_builder.cpp
+++ b/src/mongo/logger/logstream_builder.cpp
@@ -127,7 +127,7 @@ namespace logger {
         if (_os) {
             if ( !_baseMessage.empty() ) _baseMessage.push_back(' ');
             _baseMessage += _os->str();
-            MessageEventEphemeral message(curTimeMillis64(), _severity, _component, _contextName,
+            MessageEventEphemeral message(Date_t::now(), _severity, _component, _contextName,
                                           _baseMessage);
             _domain->append(message);
             if (_tee) {
diff --git a/src/mongo/logger/logstream_builder.h b/src/mongo/logger/logstream_builder.h
index 7c923d6ece3..638534484ee 100644
--- a/src/mongo/logger/logstream_builder.h
+++ b/src/mongo/logger/logstream_builder.h
@@ -35,6 +35,7 @@
 #include "mongo/logger/log_component.h"
 #include "mongo/logger/log_severity.h"
 #include "mongo/logger/message_log_domain.h"
+#include "mongo/stdx/chrono.h"
 #include "mongo/util/exit_code.h"
 
 namespace mongo {
@@ -130,6 +131,12 @@ namespace logger {
         LogstreamBuilder& operator<<(unsigned long long x) { stream() << x; return *this; }
         LogstreamBuilder& operator<<(bool x) { stream() << x; return *this; }
 
+        template <typename Rep, typename Period>
+        LogstreamBuilder& operator<<(stdx::chrono::duration<Rep, Period> d) {
+            stream() << d;
+            return *this;
+        }
+
         template <typename T>
         LogstreamBuilder& operator<<(const T& x) {
             stream() << x.toString();
diff --git a/src/mongo/logger/message_event.h b/src/mongo/logger/message_event.h
index b38e792dcd1..516af0f3f84 100644
--- a/src/mongo/logger/message_event.h
+++ b/src/mongo/logger/message_event.h
@@ -67,7 +67,7 @@ namespace logger {
             _contextName(contextName),
             _message(message) {}
 
-        uint64_t getDate() const { return _date; }
+        Date_t getDate() const { return _date; }
         LogSeverity getSeverity() const { return _severity; }
         LogComponent getComponent() const { return _component; }
         StringData getContextName() const { return _contextName; }
diff --git a/src/mongo/s/catalog/legacy/catalog_manager_legacy.cpp b/src/mongo/s/catalog/legacy/catalog_manager_legacy.cpp
index f4fb009e9df..fd8adeec67f 100644
--- a/src/mongo/s/catalog/legacy/catalog_manager_legacy.cpp
+++ b/src/mongo/s/catalog/legacy/catalog_manager_legacy.cpp
@@ -1479,7 +1479,7 @@ namespace {
             lk.lock();
             _consistentFromLastCheck = isConsistent;
             if (_inShutdown) break;
-            _consistencyCheckerCV.timed_wait(lk, Seconds(60));
+            _consistencyCheckerCV.wait_for(lk, Seconds(60));
         }
         LOG(1) << "Consistency checker thread shutting down";
     }
diff --git a/src/mongo/s/catalog/legacy/cluster_client_internal.cpp b/src/mongo/s/catalog/legacy/cluster_client_internal.cpp
index 020ab7ec5a2..96c1e4ab998 100644
--- a/src/mongo/s/catalog/legacy/cluster_client_internal.cpp
+++ b/src/mongo/s/catalog/legacy/cluster_client_internal.cpp
@@ -91,19 +91,18 @@ namespace mongo {
 
                 Date_t lastPing = ping.getPing();
 
-                long long quietIntervalMillis = 0;
+                Minutes quietIntervalMins{0};
                 Date_t currentJsTime = jsTime();
                 if (currentJsTime >= lastPing) {
-                    quietIntervalMillis = static_cast<long long>(currentJsTime - lastPing);
+                    quietIntervalMins = duration_cast<Minutes>(currentJsTime - lastPing);
                 }
-                long long quietIntervalMins = quietIntervalMillis / (60 * 1000);
 
                 // We assume that anything that hasn't pinged in 5 minutes is probably down
-                if (quietIntervalMins >= 5) {
-                    log() << "stale mongos detected " << quietIntervalMins << " minutes ago,"
-                          << " network location is " << pingDoc["_id"].String()
-                          << ", not checking version" << endl;
-            	}
+                if (quietIntervalMins >= Minutes{5}) {
+                    log() << "stale mongos detected " << quietIntervalMins.count()
+                          << " minutes ago, network location is " << pingDoc["_id"].String()
+                          << ", not checking version";
+                }
                 else {
                     if (versionCmp(mongoVersion, minMongoVersion) < 0) {
                         return Status(ErrorCodes::RemoteValidationError,
diff --git a/src/mongo/s/catalog/legacy/distlock.cpp b/src/mongo/s/catalog/legacy/distlock.cpp
index 01d3b9b005a..d55e7cb87b7 100644
--- a/src/mongo/s/catalog/legacy/distlock.cpp
+++ b/src/mongo/s/catalog/legacy/distlock.cpp
@@ -169,7 +169,7 @@ namespace mongo {
         bool success = false;
         BSONObj result;
         string errMsg;
-        long long delay = 0;
+        Milliseconds delay{0};
 
         scoped_ptr<ScopedDbConnection> connPtr;
         try {
@@ -204,7 +204,7 @@ namespace mongo {
 
         // Make sure that our delay is not more than 2x our maximum network skew, since this is the max our remote
         // time value can be off by if we assume a response in the middle of the delay.
-        if ( delay > (long long) ( maxNetSkew * 2 ) ) {
+        if (delay > Milliseconds(maxNetSkew * 2)) {
             throw TimeNotFoundException( str::stream()
                                              << "server " << server.toString() << " in cluster "
                                              << cluster.toString()
@@ -245,9 +245,10 @@ namespace mongo {
                 // Remote time can be delayed by at most MAX_NET_SKEW
 
                 // Skew is how much time we'd have to add to local to get to remote
-                avgSkews[s] += (long long) (remote - local);
+                avgSkews[s] += (remote - local).count();
 
-                LOG( logLvl + 1 ) << "skew from remote server " << server << " found: " << (long long) (remote - local) << endl;
+                LOG( logLvl + 1 ) << "skew from remote server " << server << " found: "
+                                  << (remote - local).count();
 
             }
         }
@@ -387,7 +388,7 @@ namespace mongo {
                     LOG( logLvl ) << "empty ping found for process in lock '" << lockName << "'" << endl;
                     // TODO:  Using 0 as a "no time found" value Will fail if dates roll over, but then, so will a lot.
                     lastPing = BSON( LockpingsType::process(o[LocksType::process()].String()) <<
-                                     LockpingsType::ping((Date_t) 0) );
+                                     LockpingsType::ping(Date_t()) );
                 }
 
                 unsigned long long elapsed = 0;
@@ -422,7 +423,7 @@ namespace mongo {
                         if(_lastPingCheck.remote >= remote)
                             elapsed = 0;
                         else
-                            elapsed = remote - _lastPingCheck.remote;
+                            elapsed = (remote - _lastPingCheck.remote).count();
                     }
                 }
                 catch( LockException& e ) {
diff --git a/src/mongo/s/catalog/legacy/distlock.h b/src/mongo/s/catalog/legacy/distlock.h
index 98602448642..a9667307414 100644
--- a/src/mongo/s/catalog/legacy/distlock.h
+++ b/src/mongo/s/catalog/legacy/distlock.h
@@ -129,9 +129,7 @@ namespace mongo {
                 : id(_id), lastPing(_lastPing), remote(_remote), ts(_ts){
             }
 
-            PingData()
-                : id(""), lastPing(0), remote(0), ts(){
-            }
+            PingData() : id(""), ts() {}
 
             std::string id;
             Date_t lastPing;
diff --git a/src/mongo/s/catalog/legacy/legacy_dist_lock_pinger.cpp b/src/mongo/s/catalog/legacy/legacy_dist_lock_pinger.cpp
index d8c5f3c1fe6..a6ac69f3162 100644
--- a/src/mongo/s/catalog/legacy/legacy_dist_lock_pinger.cpp
+++ b/src/mongo/s/catalog/legacy/legacy_dist_lock_pinger.cpp
@@ -53,7 +53,7 @@ namespace {
 
     void LegacyDistLockPinger::_distLockPingThread(ConnectionString addr,
                                                    const string& process,
-                                                   stdx::chrono::milliseconds sleepTime) {
+                                                   Milliseconds sleepTime) {
         setThreadName("LockPinger");
 
         string pingId = pingThreadId(addr, process);
@@ -73,11 +73,11 @@ namespace {
                 ScopedDbConnection conn(addr.toString(), 30.0);
 
                 pingTime = jsTime();
-                Date_t elapsed(pingTime.millis - lastPingTime.millis);
-                if (elapsed.millis > static_cast<unsigned long long>(10 * sleepTime.count())) {
+                const auto  elapsed = pingTime - lastPingTime;
+                if (elapsed > 10 * sleepTime) {
                     warning() << "Lock pinger for addr: " << addr
                               << ", proc: " << process
-                              << " was inactive for " << elapsed.millis << " ms";
+                              << " was inactive for " << elapsed;
                 }
 
                 lastPingTime = pingTime;
@@ -133,7 +133,7 @@ namespace {
                 // of another pinger is too skewed). This is still fine as the lock logic only
                 // checks if there is a change in the ping document and the document going away
                 // is a valid change.
-                Date_t fourDays = pingTime - (4 * 86400 * 1000); // 4 days
+                Date_t fourDays = pingTime - stdx::chrono::hours{4 * 24};
                 conn->remove(LockpingsType::ConfigNS,
                              BSON(LockpingsType::process() << NIN << pids
                                   << LockpingsType::ping() << LT << fourDays));
diff --git a/src/mongo/s/catalog/legacy/legacy_dist_lock_pinger.h b/src/mongo/s/catalog/legacy/legacy_dist_lock_pinger.h
index 6d0ac4ebf6f..e7dec414bb9 100644
--- a/src/mongo/s/catalog/legacy/legacy_dist_lock_pinger.h
+++ b/src/mongo/s/catalog/legacy/legacy_dist_lock_pinger.h
@@ -36,9 +36,9 @@
 #include "mongo/base/status.h"
 #include "mongo/client/dbclientinterface.h"
 #include "mongo/s/catalog/dist_lock_manager.h"
-#include "mongo/stdx/chrono.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/util/concurrency/mutex.h"
+#include "mongo/util/time_support.h"
 
 namespace mongo {
 
@@ -51,7 +51,7 @@ namespace mongo {
         /**
          * Starts pinging the process id for the given lock.
          */
-        Status startPing(const DistributedLock& lock, stdx::chrono::milliseconds sleepTime);
+        Status startPing(const DistributedLock& lock, Milliseconds sleepTime);
 
         /**
          * Adds a distributed lock that has the given id to the unlock list. The unlock list
@@ -82,7 +82,7 @@ namespace mongo {
         void distLockPingThread(ConnectionString addr,
                                 long long clockSkew,
                                 const std::string& processId,
-                                stdx::chrono::milliseconds sleepTime);
+                                Milliseconds sleepTime);
 
         /**
          * Function for repeatedly pinging the process id. Also attempts to unlock all the
@@ -90,7 +90,7 @@ namespace mongo {
          */
         void _distLockPingThread(ConnectionString addr,
                                  const std::string& process,
-                                 stdx::chrono::milliseconds sleepTime);
+                                 Milliseconds sleepTime);
 
         /**
          * Returns true if a request has been made to stop pinging the give process id.
@@ -105,7 +105,7 @@ namespace mongo {
         /**
          * Blocks until duration has elapsed or if the ping thread is interrupted.
          */
-        void waitTillNextPingTime(stdx::chrono::milliseconds duration);
+        void waitTillNextPingTime(Milliseconds duration);
 
         //
         // All member variables are labeled with one of the following codes indicating the
diff --git a/src/mongo/s/catalog/type_actionlog.cpp b/src/mongo/s/catalog/type_actionlog.cpp
index 8d208778e0f..49dd09b6958 100644
--- a/src/mongo/s/catalog/type_actionlog.cpp
+++ b/src/mongo/s/catalog/type_actionlog.cpp
@@ -123,7 +123,7 @@ namespace mongo {
         _what.clear();
         _isWhatSet = false;
 
-        _time = 0ULL;
+        _time = Date_t();
         _isTimeSet = false;
 
         _details = BSONObj();
diff --git a/src/mongo/s/catalog/type_changelog.cpp b/src/mongo/s/catalog/type_changelog.cpp
index f73b90f72c0..40db60dbf94 100644
--- a/src/mongo/s/catalog/type_changelog.cpp
+++ b/src/mongo/s/catalog/type_changelog.cpp
@@ -158,7 +158,7 @@ namespace mongo {
         _clientAddr.clear();
         _isClientAddrSet = false;
 
-        _time = 0ULL;
+        _time = Date_t();
         _isTimeSet = false;
 
         _what.clear();
diff --git a/src/mongo/s/catalog/type_collection.cpp b/src/mongo/s/catalog/type_collection.cpp
index 9656daf9886..9fbfb824add 100644
--- a/src/mongo/s/catalog/type_collection.cpp
+++ b/src/mongo/s/catalog/type_collection.cpp
@@ -163,7 +163,7 @@ namespace mongo {
                 return Status(ErrorCodes::BadValue, "invalid epoch");
             }
 
-            if (!_updatedAt.get()) {
+            if (Date_t() == _updatedAt.get()) {
                 return Status(ErrorCodes::BadValue, "invalid updated at timestamp");
             }
 
@@ -183,7 +183,7 @@ namespace mongo {
 
         builder.append(fullNs.name(), _fullNs.get_value_or(""));
         builder.append(epoch.name(), _epoch.get_value_or(OID()));
-        builder.append(updatedAt.name(), _updatedAt.get_value_or(0));
+        builder.append(updatedAt.name(), _updatedAt.get_value_or(Date_t()));
 
         // These fields are optional, so do not include them in the metadata for the purposes of
         // consuming less space on the config servers.
diff --git a/src/mongo/s/chunk_version.h b/src/mongo/s/chunk_version.h
index 258097ec9cf..41b9e03bae2 100644
--- a/src/mongo/s/chunk_version.h
+++ b/src/mongo/s/chunk_version.h
@@ -78,7 +78,7 @@ namespace mongo {
 
         static ChunkVersion IGNORED() {
             ChunkVersion version = ChunkVersion();
-            version._epoch.init( 0, true ); // ignored OID is zero time, max machineId/inc
+            version._epoch.init(Date_t(), true); // ignored OID is zero time, max machineId/inc
             return version;
         }
 
diff --git a/src/mongo/s/client/multi_host_query.cpp b/src/mongo/s/client/multi_host_query.cpp
index b3b5727ee6c..294cfce2afd 100644
--- a/src/mongo/s/client/multi_host_query.cpp
+++ b/src/mongo/s/client/multi_host_query.cpp
@@ -181,7 +181,7 @@ namespace mongo {
                                                            int timeoutMillis) {
 
         Date_t nowMillis = _systemEnv->currentTimeMillis();
-        Date_t timeoutAtMillis = nowMillis + timeoutMillis;
+        Date_t timeoutAtMillis = nowMillis + Milliseconds(timeoutMillis);
 
         // Send out all queries
         scheduleQuery(hosts, query, timeoutAtMillis);
@@ -228,8 +228,7 @@ namespace mongo {
                 break;
             }
 
-            _nextResultCV.timed_wait(lk,
-                                     boost::posix_time::milliseconds(timeoutAtMillis - nowMillis));
+            _nextResultCV.wait_for(lk, timeoutAtMillis - nowMillis);
         }
 
         dassert( !nextResult.isOK() || nextResult.getValue() );
diff --git a/src/mongo/s/type_lockpings.cpp b/src/mongo/s/type_lockpings.cpp
index 853a76dd010..47beaea1485 100644
--- a/src/mongo/s/type_lockpings.cpp
+++ b/src/mongo/s/type_lockpings.cpp
@@ -99,7 +99,7 @@ namespace mongo {
         _process.clear();
         _isProcessSet = false;
 
-        _ping = 0ULL;
+        _ping = Date_t();
         _isPingSet = false;
 
     }
diff --git a/src/mongo/s/type_mongos.cpp b/src/mongo/s/type_mongos.cpp
index 0ff363cbc86..07009c6a864 100644
--- a/src/mongo/s/type_mongos.cpp
+++ b/src/mongo/s/type_mongos.cpp
@@ -131,7 +131,7 @@ namespace mongo {
         _name.clear();
         _isNameSet = false;
 
-        _ping = 0ULL;
+        _ping = Date_t();
         _isPingSet = false;
 
         _up = 0;
diff --git a/src/mongo/s/version_manager.cpp b/src/mongo/s/version_manager.cpp
index 102bd720643..f5437543afb 100644
--- a/src/mongo/s/version_manager.cpp
+++ b/src/mongo/s/version_manager.cpp
@@ -402,7 +402,7 @@ namespace mongo {
         }
         
         if ( result["reloadConfig"].trueValue() ) {
-            if( result["version"].timestampTime() == 0 ){
+            if( result["version"].timestampTime() == Date_t() ){
 
                 warning() << "reloading full configuration for " << conf->name()
                           << ", connection state indicates significant version changes";
diff --git a/src/mongo/scripting/engine.cpp b/src/mongo/scripting/engine.cpp
index a3178880ea5..675c8e8600b 100644
--- a/src/mongo/scripting/engine.cpp
+++ b/src/mongo/scripting/engine.cpp
@@ -109,8 +109,9 @@ namespace {
             builder.appendNull(fieldName);
             break;
         case Date:
-            // TODO: make signed
-            builder.appendDate(fieldName, Date_t((unsigned long long)getNumber(scopeName)));
+            builder.appendDate(fieldName,
+                               Date_t::fromMillisSinceEpoch(static_cast<long long>(
+                                                                    getNumber(scopeName))));
             break;
         case Code:
             builder.appendCode(fieldName, getString(scopeName));
diff --git a/src/mongo/scripting/engine_v8-3.25.cpp b/src/mongo/scripting/engine_v8-3.25.cpp
index cd8ff7aceeb..9b2f82fe359 100644
--- a/src/mongo/scripting/engine_v8-3.25.cpp
+++ b/src/mongo/scripting/engine_v8-3.25.cpp
@@ -1507,7 +1507,7 @@ namespace mongo {
         case mongo::Object:
             return mongoToLZV8(elem.embeddedObject(), readOnly);
         case mongo::Date:
-            return v8::Date::New(_isolate, (double) ((long long)elem.date().millis));
+            return v8::Date::New(_isolate, static_cast<double>(elem.date.toMillisSinceEpoch()));
         case mongo::Bool:
             return v8::Boolean::New(_isolate, elem.boolean());
         case mongo::EOO:
diff --git a/src/mongo/scripting/engine_v8.cpp b/src/mongo/scripting/engine_v8.cpp
index 242e39be1a4..50477bbfb99 100644
--- a/src/mongo/scripting/engine_v8.cpp
+++ b/src/mongo/scripting/engine_v8.cpp
@@ -1435,7 +1435,7 @@ namespace mongo {
         case mongo::Object:
             return mongoToLZV8(elem.embeddedObject(), readOnly);
         case mongo::Date:
-            return v8::Date::New((double) ((long long)elem.date().millis));
+            return v8::Date::New(static_cast<double>(elem.date().toMillisSinceEpoch()));
         case mongo::Bool:
             return v8::Boolean::New(elem.boolean());
         case mongo::EOO:
@@ -1472,7 +1472,7 @@ namespace mongo {
         case mongo::bsonTimestamp: {
             v8::TryCatch tryCatch;
 
-            argv[0] = v8::Number::New(elem.timestampTime() / 1000);
+            argv[0] = v8::Number::New(elem.timestampTime().toMillisSinceEpoch() / 1000);
             argv[1] = v8::Number::New(elem.timestampInc());
 
             v8::Handle<v8::Value> ret = TimestampFT()->GetFunction()->NewInstance(2,argv);
@@ -1658,7 +1658,7 @@ namespace mongo {
         }
         if (value->IsDate()) {
             long long dateval = (long long)(v8::Date::Cast(*value)->NumberValue());
-            b.appendDate(sname, Date_t((unsigned long long) dateval));
+            b.appendDate(sname, Date_t::fromMillisSinceEpoch(dateval));
             return;
         }
         if (value->IsExternal())
diff --git a/src/mongo/unittest/unittest_helpers.h b/src/mongo/unittest/unittest_helpers.h
index 97ab7cc1efe..44abea5e8d6 100644
--- a/src/mongo/unittest/unittest_helpers.h
+++ b/src/mongo/unittest/unittest_helpers.h
@@ -32,7 +32,7 @@
 
 namespace mongo {
     class Timestamp;
-    struct Date_t;
+    class Date_t;
 
     // So that you can ASSERT_EQUALS two Timestamps
     std::ostream& operator<<(std::ostream& s, const Timestamp& ot);
diff --git a/src/mongo/util/net/ssl_expiration.cpp b/src/mongo/util/net/ssl_expiration.cpp
index 9f1d6ef9676..d05462ce442 100644
--- a/src/mongo/util/net/ssl_expiration.cpp
+++ b/src/mongo/util/net/ssl_expiration.cpp
@@ -32,14 +32,15 @@
 #include <string>
 
 #include "mongo/util/log.h"
+#include "mongo/util/time_support.h"
 
 namespace mongo {
 
-    static const unsigned long long dayInMillis = 24 * 60 * 60 * 1000;
+    static const auto oneDay = stdx::chrono::hours(24);
 
     CertificateExpirationMonitor::CertificateExpirationMonitor(Date_t date)
         : _certExpiration(date)
-        , _lastCheckTime(Date_t(curTimeMillis64())) {
+        , _lastCheckTime(Date_t::now()) {
     }
 
     std::string CertificateExpirationMonitor::taskName() const {
@@ -47,30 +48,28 @@ namespace mongo {
     }
 
     void CertificateExpirationMonitor::taskDoWork() {
-        const unsigned long long timeSinceLastCheck = 
-            curTimeMillis64() - _lastCheckTime.millis;
+        const Milliseconds timeSinceLastCheck = Date_t::now() - _lastCheckTime;
 
-        if (timeSinceLastCheck < dayInMillis)
+        if (timeSinceLastCheck < oneDay)
             return;
 
-        const Date_t now = Date_t(curTimeMillis64());
+        const Date_t now = Date_t::now();
         _lastCheckTime = now;
 
-        if (_certExpiration.millis <= now.millis) {
+        if (_certExpiration <= now) {
             // The certificate has expired.
             warning() << "Server certificate is now invalid. It expired on "
-                      << dateToCtimeString(_certExpiration);
+                      << dateToISOStringUTC(_certExpiration);
             return;
         }
 
-        const unsigned long long remainingValidMillis =
-            _certExpiration.millis - now.millis;
+        const auto remainingValidDuration = _certExpiration - now;
 
-        if (remainingValidMillis / dayInMillis <= 30) {
+        if (remainingValidDuration <= 30 * oneDay) {
             // The certificate will expire in the next 30 days.
             warning() << "Server certificate will expire on "
-                      << dateToCtimeString(_certExpiration) << " in "
-                      << (remainingValidMillis / dayInMillis)
+                      << dateToISOStringUTC(_certExpiration) << " in "
+                      << durationCount<stdx::chrono::hours>(remainingValidDuration) / 24
                       << " days.";
         }
     }
diff --git a/src/mongo/util/net/ssl_manager.cpp b/src/mongo/util/net/ssl_manager.cpp
index 6f9be1a1c03..652807e7e71 100644
--- a/src/mongo/util/net/ssl_manager.cpp
+++ b/src/mongo/util/net/ssl_manager.cpp
@@ -699,7 +699,7 @@ namespace mongo {
                        "The provided SSL certificate is expired or not yet valid.");
             }
 
-            *serverCertificateExpirationDate = Date_t(notAfterMillis);
+            *serverCertificateExpirationDate = Date_t::fromMillisSinceEpoch(notAfterMillis);
         }
 
         return true;
diff --git a/src/mongo/util/signal_handlers_synchronous.cpp b/src/mongo/util/signal_handlers_synchronous.cpp
index e28d2796fd5..e0d69350203 100644
--- a/src/mongo/util/signal_handlers_synchronous.cpp
+++ b/src/mongo/util/signal_handlers_synchronous.cpp
@@ -114,7 +114,7 @@ namespace {
     // must hold streamMutex to call
     void writeMallocFreeStreamToLog() {
         logger::globalLogDomain()->append(
-            logger::MessageEventEphemeral(curTimeMillis64(),
+            logger::MessageEventEphemeral(Date_t::now(),
                                           logger::LogSeverity::Severe(),
                                           getThreadName(),
                                           mallocFreeOStream.str()));
diff --git a/src/mongo/util/time_support.cpp b/src/mongo/util/time_support.cpp
index 69369582058..a850e7fceac 100644
--- a/src/mongo/util/time_support.cpp
+++ b/src/mongo/util/time_support.cpp
@@ -41,6 +41,7 @@
 #include "mongo/bson/util/builder.h"
 #include "mongo/platform/cstdint.h"
 #include "mongo/util/assert_util.h"
+#include "mongo/util/mongoutils/str.h"
 
 #ifdef _WIN32
 #include <boost/date_time/filetime_functions.hpp>
@@ -64,12 +65,73 @@ timegm(struct tm *const tmp);
 
 namespace mongo {
 
+namespace {
+    template <typename Stream> Stream& streamPut(Stream& os, Microseconds us) {
+        return os << us.count() << "\xce\xbcs";
+    }
+
+    template <typename Stream> Stream& streamPut(Stream& os, Milliseconds ms) {
+        return os << ms.count() << "ms";
+    }
+
+    template <typename Stream> Stream& streamPut(Stream& os, Seconds s) {
+         return os << s.count() << 's';
+    }
+} // namespace
+
+    std::ostream& operator<<(std::ostream& os, Microseconds us) {
+        return streamPut(os, us);
+    }
+
+    std::ostream& operator<<(std::ostream& os, Milliseconds ms) {
+        return streamPut(os, ms);
+    }
+    std::ostream& operator<<(std::ostream& os, Seconds s) {
+        return streamPut(os, s);
+    }
+
+    template <typename Allocator>
+    StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& os, Microseconds us) {
+        return streamPut(os, us);
+    }
+
+    template <typename Allocator>
+    StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& os, Milliseconds ms) {
+        return streamPut(os, ms);
+    }
+
+    template <typename Allocator>
+    StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& os, Seconds s) {
+        return streamPut(os, s);
+    }
+
+    template StringBuilderImpl<StackAllocator>& operator<<(StringBuilderImpl<StackAllocator>&,
+                                                           Microseconds);
+    template StringBuilderImpl<StackAllocator>& operator<<(StringBuilderImpl<StackAllocator>&,
+                                                           Milliseconds);
+    template StringBuilderImpl<StackAllocator>& operator<<(StringBuilderImpl<StackAllocator>&,
+                                                           Seconds);
+    template StringBuilderImpl<TrivialAllocator>& operator<<(StringBuilderImpl<TrivialAllocator>&,
+                                                             Microseconds);
+    template StringBuilderImpl<TrivialAllocator>& operator<<(StringBuilderImpl<TrivialAllocator>&,
+                                                             Milliseconds);
+    template StringBuilderImpl<TrivialAllocator>& operator<<(StringBuilderImpl<TrivialAllocator>&,
+                                                             Seconds);
+
+    Date_t Date_t::max() {
+        return fromMillisSinceEpoch(std::numeric_limits<long long>::max());
+    }
+
+    Date_t Date_t::now() {
+        return fromMillisSinceEpoch(curTimeMillis64());
+    }
+
     bool Date_t::isFormatable() const {
         if (sizeof(time_t) == sizeof(int32_t)) {
-            return millis < 2147483647000ULL; // "2038-01-19T03:14:07Z"
+            return millis < 2147483647000LL; // "2038-01-19T03:14:07Z"
         }
         else {
-            return millis < 32535215999000ULL; // "3000-12-31T23:59:59Z"
+            return millis < 32535215999000LL; // "3000-12-31T23:59:59Z"
         }
     }
 
@@ -690,7 +752,11 @@ namespace {
 
         resultMillis += (tzAdjSecs * 1000);
 
-        return StatusWith<Date_t>(resultMillis);
+        if (resultMillis > static_cast<unsigned long long>(std::numeric_limits<long long>::max())) {
+            return {ErrorCodes::BadValue,
+                    str::stream() << dateString << " is too far in the future"};
+        }
+        return Date_t::fromMillisSinceEpoch(static_cast<long long>(resultMillis));
     }
 
 #undef MONGO_ISO_DATE_FMT_NO_TZ
@@ -976,11 +1042,11 @@ namespace {
         return ((unsigned long long)tv.tv_sec) * 1000 + tv.tv_usec / 1000;
     }
     Date_t jsTime() {
-        timeval tv;
-        gettimeofday(&tv, NULL);
-        unsigned long long t = tv.tv_usec / 1000;
-        return ((unsigned long long) tv.tv_sec * 1000) + t + getJSTimeVirtualSkew() + getJSTimeVirtualThreadSkew();
+        return Date_t::now() +
+            Milliseconds(getJSTimeVirtualThreadSkew()) +
+            Milliseconds(getJSTimeVirtualSkew());
     }
+
     unsigned long long curTimeMicros64() {
         timeval tv;
         gettimeofday(&tv, NULL);
diff --git a/src/mongo/util/time_support.h b/src/mongo/util/time_support.h
index 81db17cbd76..988453f6c39 100644
--- a/src/mongo/util/time_support.h
+++ b/src/mongo/util/time_support.h
@@ -37,30 +37,116 @@
 #include <boost/version.hpp>
 
 #include "mongo/base/status_with.h"
+#include "mongo/stdx/chrono.h"
 
 namespace mongo {
 
-    typedef boost::posix_time::milliseconds Milliseconds;
-    typedef boost::posix_time::seconds Seconds;
+    template <typename Allocator> class StringBuilderImpl;
+
+    using Microseconds = stdx::chrono::microseconds;
+    using Milliseconds = stdx::chrono::milliseconds;
+    using Seconds = stdx::chrono::seconds;
+    using Minutes = stdx::chrono::minutes;
+    using stdx::chrono::duration_cast;
 
     void time_t_to_Struct(time_t t, struct tm * buf , bool local = false );
     std::string time_t_to_String(time_t t);
     std::string time_t_to_String_short(time_t t);
 
-    struct Date_t {
-        // TODO: make signed (and look for related TODO's)
-        unsigned long long millis;
+    //
+    // Operators for putting durations to streams.
+    //
+
+    std::ostream& operator<<(std::ostream& os, Microseconds us);
+    std::ostream& operator<<(std::ostream& os, Milliseconds ms);
+    std::ostream& operator<<(std::ostream& os, Seconds s);
+
+    template <typename Allocator>
+    StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& os, Microseconds us);
+
+    template <typename Allocator>
+    StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& os, Milliseconds ms);
+
+    template <typename Allocator>
+    StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& os, Seconds s);
+
+    /**
+     * Convenience method for reading the count of a duration with specified units.
+     *
+     * Use when logging or comparing to integers, to ensure that you're using
+     * the units you intend.
+     *
+     * E.g., log() << durationCount<Seconds>(some duration) << " seconds";
+     */
+    template <typename DOut, typename DIn> long long durationCount(DIn d) {
+        return duration_cast<DOut>(d).count();
+    }
+
+    class Date_t {
+    public:
+        static Date_t max();
+        static Date_t now();
+
+        static Date_t fromMillisSinceEpoch(long long m) {
+            return Date_t(m);
+        }
+
+        template <typename Duration>
+        static Date_t fromDurationSinceEpoch(Duration d) {
+            return fromMillisSinceEpoch(durationCount<Milliseconds>(d));
+        }
+
         Date_t(): millis(0) {}
-        Date_t(unsigned long long m): millis(m) {}
-        operator unsigned long long&() { return millis; }
-        operator const unsigned long long&() const { return millis; }
+
         void toTm (tm *buf);
         std::string toString() const;
         time_t toTimeT() const;
         int64_t asInt64() const {
-            return static_cast<int64_t>(millis);
+            return toMillisSinceEpoch();
         }
+        unsigned long long toULL() const { return static_cast<unsigned long long>(asInt64()); }
+        Milliseconds toDurationSinceEpoch() const { return Milliseconds(toMillisSinceEpoch()); }
+        long long toMillisSinceEpoch() const { return static_cast<long long>(millis); }
         bool isFormatable() const;
+
+        template <typename Duration>
+        Date_t operator+(Duration d) const {
+            return { millis + duration_cast<Milliseconds>(d).count() };
+        }
+
+        template <typename Duration>
+        Date_t operator-(Duration d) const {
+            return *this + (-d);
+        }
+
+        Milliseconds operator-(Date_t other) const { return Milliseconds(millis - other.millis); }
+
+        bool operator==(Date_t other) const {
+            return toDurationSinceEpoch() == other.toDurationSinceEpoch();
+        }
+
+        bool operator!=(Date_t other) const { return !(*this == other); }
+
+        bool operator<(Date_t other) const {
+            return toDurationSinceEpoch() < other.toDurationSinceEpoch();
+        }
+
+        bool operator>(Date_t other) const {
+            return toDurationSinceEpoch() > other.toDurationSinceEpoch();
+        }
+
+        bool operator<=(Date_t other) const {
+            return !(*this > other);
+        }
+
+        bool operator>=(Date_t other) const {
+            return !(*this < other);
+        }
+
+    private:
+        Date_t(long long m): millis(m) {}
+
+        long long millis;
     };
 
     // uses ISO 8601 dates without trailing Z
diff --git a/src/mongo/util/time_support_test.cpp b/src/mongo/util/time_support_test.cpp
index 0580584c62e..dc367e61647 100644
--- a/src/mongo/util/time_support_test.cpp
+++ b/src/mongo/util/time_support_test.cpp
@@ -813,5 +813,15 @@ namespace {
         }
     }
 
+    TEST(TimeFormatting, DurationFormatting) {
+        ASSERT_EQUALS("52\xce\xbcs", static_cast<std::string>(str::stream() << Microseconds(52)));
+        ASSERT_EQUALS("52ms", static_cast<std::string>(str::stream() << Milliseconds(52)));
+        ASSERT_EQUALS("52s", static_cast<std::string>(str::stream() << Seconds(52)));
+
+        std::ostringstream os;
+        os << Milliseconds(52) << Microseconds(52) << Seconds(52);
+        ASSERT_EQUALS("52ms52\xce\xbcs52s", os.str());
+    }
+
 }  // namespace
 }  // namespace mongo