SERVER-47030 Fix date_time_support to not throw exceptions

5 files changed, 236 insertions, 126 deletions

diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index 51a284e6a52..33659fe89e2 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -1873,10 +1873,12 @@ Value ExpressionDateToString::evaluate(const Document& root, Variables* variable
             return Value(BSONNULL);
         }
 
-        return Value(timeZone->formatDate(formatValue.getStringData(), date.coerceToDate()));
+        return Value(uassertStatusOK(
+            timeZone->formatDate(formatValue.getStringData(), date.coerceToDate())));
     }
 
-    return Value(timeZone->formatDate(Value::kISOFormatString, date.coerceToDate()));
+    return Value(
+        uassertStatusOK(timeZone->formatDate(Value::kISOFormatString, date.coerceToDate())));
 }
 
 void ExpressionDateToString::_doAddDependencies(DepsTracker* deps) const {
@@ -5178,8 +5180,8 @@ public:
             };
         table[BSONType::Date][BSONType::String] =
             [](const boost::intrusive_ptr<ExpressionContext>& expCtx, Value inputValue) {
-                auto dateString = TimeZoneDatabase::utcZone().formatDate(Value::kISOFormatString,
-                                                                         inputValue.getDate());
+                auto dateString = uassertStatusOK(TimeZoneDatabase::utcZone().formatDate(
+                    Value::kISOFormatString, inputValue.getDate()));
                 return Value(dateString);
             };
         table[BSONType::Date]
diff --git a/src/mongo/db/pipeline/value.cpp b/src/mongo/db/pipeline/value.cpp
index 065a7e12f67..ef3451191bc 100644
--- a/src/mongo/db/pipeline/value.cpp
+++ b/src/mongo/db/pipeline/value.cpp
@@ -58,6 +58,7 @@ using std::ostream;
 using std::string;
 using std::stringstream;
 using std::vector;
+using namespace std::string_literals;
 
 constexpr StringData Value::kISOFormatString;
 
@@ -628,7 +629,9 @@ string Value::coerceToString() const {
             return getTimestamp().toStringPretty();
 
         case Date:
-            return TimeZoneDatabase::utcZone().formatDate(Value::kISOFormatString, getDate());
+            return uassertStatusOKWithContext(
+                TimeZoneDatabase::utcZone().formatDate(Value::kISOFormatString, getDate()),
+                "failed while coercing date to string");
 
         case EOO:
         case jstNULL:
@@ -1164,8 +1167,14 @@ ostream& operator<<(ostream& out, const Value& val) {
         case Undefined:
             return out << "undefined";
         case Date:
-            return out << TimeZoneDatabase::utcZone().formatDate(Value::kISOFormatString,
-                                                                 val.coerceToDate());
+            return out << [&] {
+                auto string = TimeZoneDatabase::utcZone().formatDate(Value::kISOFormatString,
+                                                                     val.coerceToDate());
+                if (string.isOK())
+                    return string.getValue();
+                else
+                    return "illegal date"s;
+            }();
         case bsonTimestamp:
             return out << val.getTimestamp().toString();
         case Object:
diff --git a/src/mongo/db/query/datetime/date_time_support.cpp b/src/mongo/db/query/datetime/date_time_support.cpp
index 478efe044be..76002d0d87d 100644
--- a/src/mongo/db/query/datetime/date_time_support.cpp
+++ b/src/mongo/db/query/datetime/date_time_support.cpp
@@ -558,9 +558,12 @@ void TimeZone::validateFromStringFormat(StringData format) {
     return validateFormat(format, kDateFromStringFormatMap);
 }
 
-std::string TimeZone::formatDate(StringData format, Date_t date) const {
+StatusWith<std::string> TimeZone::formatDate(StringData format, Date_t date) const {
     StringBuilder formatted;
-    outputDateWithFormat(formatted, format, date);
-    return formatted.str();
+    auto status = outputDateWithFormat(formatted, format, date);
+    if (status != Status::OK())
+        return status;
+    else
+        return formatted.str();
 }
 }  // namespace mongo
diff --git a/src/mongo/db/query/datetime/date_time_support.h b/src/mongo/db/query/datetime/date_time_support.h
index 18462f40cc3..56818020319 100644
--- a/src/mongo/db/query/datetime/date_time_support.h
+++ b/src/mongo/db/query/datetime/date_time_support.h
@@ -32,8 +32,10 @@
 
 #include <memory>
 #include <string>
+#include <utility>
 
 #include "mongo/base/disallow_copying.h"
+#include "mongo/base/status.h"
 #include "mongo/db/service_context.h"
 #include "mongo/util/string_map.h"
 #include "mongo/util/time_support.h"
@@ -45,6 +47,8 @@ struct _timelib_tzinfo;
 
 namespace mongo {
 
+using namespace std::string_literals;
+
 /**
  * A TimeZone object represents one way of formatting/reading dates to compute things like the day
  * of the week or the hour of a given date. Different TimeZone objects may report different answers
@@ -194,15 +198,15 @@ public:
      * Converts a date object to a string according to 'format'. 'format' can be any string literal,
      * containing 0 or more format specifiers like %Y (year) or %d (day of month). Callers must pass
      * a valid format string for 'format', i.e. one that has already been passed to
-     * validateFormat().
+     * validateFormat(). May return a Status indicating that the date value is an unprintable range.
      */
-    std::string formatDate(StringData format, Date_t) const;
+    StatusWith<std::string> formatDate(StringData format, Date_t) const;
 
     /**
      * Like formatDate, except outputs to an output stream like a std::ostream or a StringBuilder.
      */
     template <typename OutputStream>
-    void outputDateWithFormat(OutputStream& os, StringData format, Date_t date) const {
+    auto outputDateWithFormat(OutputStream& os, StringData format, Date_t date) const {
         auto parts = dateParts(date);
         for (auto&& it = format.begin(); it != format.end(); ++it) {
             if (*it != '%') {
@@ -219,51 +223,105 @@ public:
                     break;
                 case 'Y':  // Year
                 {
-                    insertPadded(os, parts.year, 4);
+                    auto status = insertPadded(os, parts.year, 4);
+                    if (status != Status::OK())
+                        return status;
                     break;
                 }
                 case 'm':  // Month
-                    insertPadded(os, parts.month, 2);
+                {
+                    auto status = insertPadded(os, parts.month, 2);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'd':  // Day of month
-                    insertPadded(os, parts.dayOfMonth, 2);
+                {
+                    auto status = insertPadded(os, parts.dayOfMonth, 2);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'H':  // Hour
-                    insertPadded(os, parts.hour, 2);
+                {
+                    auto status = insertPadded(os, parts.hour, 2);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'M':  // Minute
-                    insertPadded(os, parts.minute, 2);
+                {
+                    auto status = insertPadded(os, parts.minute, 2);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'S':  // Second
-                    insertPadded(os, parts.second, 2);
+                {
+                    auto status = insertPadded(os, parts.second, 2);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'L':  // Millisecond
-                    insertPadded(os, parts.millisecond, 3);
+                {
+                    auto status = insertPadded(os, parts.millisecond, 3);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'j':  // Day of year
-                    insertPadded(os, dayOfYear(date), 3);
+                {
+                    auto status = insertPadded(os, dayOfYear(date), 3);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'w':  // Day of week
-                    insertPadded(os, dayOfWeek(date), 1);
+                {
+                    auto status = insertPadded(os, dayOfWeek(date), 1);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'U':  // Week
-                    insertPadded(os, week(date), 2);
+                {
+                    auto status = insertPadded(os, week(date), 2);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'G':  // Iso year of week
-                    insertPadded(os, isoYear(date), 4);
+                {
+                    auto status = insertPadded(os, isoYear(date), 4);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'V':  // Iso week
-                    insertPadded(os, isoWeek(date), 2);
+                {
+                    auto status = insertPadded(os, isoWeek(date), 2);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'u':  // Iso day of week
-                    insertPadded(os, isoDayOfWeek(date), 1);
+                {
+                    auto status = insertPadded(os, isoDayOfWeek(date), 1);
+                    if (status != Status::OK())
+                        return status;
                     break;
+                }
                 case 'z':  // UTC offset as ±hhmm.
                 {
                     auto offset = utcOffset(date);
-                    os << ((offset.count() < 0) ? "-" : "+");                            // sign
-                    insertPadded(os, std::abs(durationCount<Hours>(offset)), 2);         // hh
-                    insertPadded(os, std::abs(durationCount<Minutes>(offset)) % 60, 2);  // mm
+                    os << ((offset.count() < 0) ? "-" : "+");  // sign
+                    auto status = insertPadded(os, std::abs(durationCount<Hours>(offset)), 2);
+                    if (status != Status::OK())  // hh
+                        return status;
+                    status = insertPadded(os, std::abs(durationCount<Minutes>(offset)) % 60, 2);
+                    if (status != Status::OK())  // mm
+                        return status;
                     break;
                 }
                 case 'Z':  // UTC offset in minutes.
@@ -274,6 +332,7 @@ public:
                     MONGO_UNREACHABLE;
             }
         }
+        return Status::OK();
     }
 
     /**
@@ -291,15 +350,15 @@ private:
      * count of number we simply insert the number without padding.
      */
     template <typename OutputStream>
-    void insertPadded(OutputStream& os, int number, int width) const {
+    static auto insertPadded(OutputStream& os, int number, int width) {
         invariant(width >= 1);
         invariant(width <= 4);
 
-        uassert(18537,
-                str::stream() << "Could not convert date to string: date component was outside "
-                              << "the supported range of 0-9999: "
-                              << number,
-                (number >= 0) && (number <= 9999));
+        if ((number < 0) || (number > 9999))
+            return Status(ErrorCodes::Error(18537),
+                          str::stream() << "Could not convert date to string: date component was "
+                                           "outside the supported range of 0-9999: "
+                                        << number);
 
         int digits = 1;
 
@@ -315,6 +374,7 @@ private:
             os.write("0000", width - digits);
         }
         os << number;
+        return Status::OK();
     }
 
     struct TimelibTZInfoDeleter {
@@ -326,7 +386,7 @@ private:
 
     // represents the UTC offset in seconds if _tzInfo is null and it is not 0
     Seconds _utcOffset{0};
-};
+};  // namespace mongo
 
 /**
  * A C++ interface wrapping the third-party timelib library. A single instance of this class can be
diff --git a/src/mongo/db/query/datetime/date_time_support_test.cpp b/src/mongo/db/query/datetime/date_time_support_test.cpp
index b8230180621..fd1e86eea97 100644
--- a/src/mongo/db/query/datetime/date_time_support_test.cpp
+++ b/src/mongo/db/query/datetime/date_time_support_test.cpp
@@ -388,12 +388,16 @@ TEST(NewYorkTimeBeforeEpoch, DoesComputeISOWeek) {
 TEST(UTCTimeBeforeEpoch, DoesFormatDate) {
     // Tuesday, Dec 30, 1969 13:42:23:211
     auto date = Date_t::fromMillisSinceEpoch(-123456789LL);
-    ASSERT_EQ(TimeZoneDatabase::utcZone().formatDate("%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                                     date),
-              "1969/12/30 13:42:23:211, dayOfYear: 364, dayOfWeek: 3, week: 52, isoYear: 1970, "
-              "isoWeek: 01, isoDayOfWeek: 2, percent: %");
+    auto result = TimeZoneDatabase::utcZone().formatDate(
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date);
+    ASSERT_OK(result);
+    ASSERT_EQ(
+        "1969/12/30 13:42:23:211, dayOfYear: 364, dayOfWeek: 3, week: 52, isoYear: 1970, "
+        "isoWeek: 01, isoDayOfWeek: 2, percent: %",
+        result.getValue());
 }
 
 TEST(NewYorkTimeBeforeEpoch, DoesFormatDate) {
@@ -401,23 +405,28 @@ TEST(NewYorkTimeBeforeEpoch, DoesFormatDate) {
 
     // Tuesday, Dec 30, 1969 13:42:23:211
     auto date = Date_t::fromMillisSinceEpoch(-123456789LL);
-    ASSERT_EQ(newYorkZone.formatDate("%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                     date),
-              "1969/12/30 08:42:23:211, dayOfYear: 364, dayOfWeek: 3, week: 52, isoYear: 1970, "
-              "isoWeek: 01, isoDayOfWeek: 2, percent: %");
+    auto result = newYorkZone.formatDate(
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date);
+    ASSERT_OK(result);
+    ASSERT_EQ(
+        "1969/12/30 08:42:23:211, dayOfYear: 364, dayOfWeek: 3, week: 52, isoYear: 1970, "
+        "isoWeek: 01, isoDayOfWeek: 2, percent: %",
+        result.getValue());
 }
 
 TEST(UTCTimeBeforeEpoch, DoesOutputFormatDate) {
     // Tuesday, Dec 30, 1969 13:42:23:211
     auto date = Date_t::fromMillisSinceEpoch(-123456789LL);
     std::ostringstream os;
-    TimeZoneDatabase::utcZone().outputDateWithFormat(os,
-                                                     "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                                     date);
+    ASSERT_OK(TimeZoneDatabase::utcZone().outputDateWithFormat(
+        os,
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date));
     ASSERT_EQ(os.str(),
               "1969/12/30 13:42:23:211, dayOfYear: 364, dayOfWeek: 3, week: 52, isoYear: 1970, "
               "isoWeek: 01, isoDayOfWeek: 2, percent: %");
@@ -429,11 +438,11 @@ TEST(NewYorkTimeBeforeEpoch, DoesOutputFormatDate) {
     // Tuesday, Dec 30, 1969 13:42:23:211
     auto date = Date_t::fromMillisSinceEpoch(-123456789LL);
     std::ostringstream os;
-    newYorkZone.outputDateWithFormat(os,
-                                     "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                     date);
+    ASSERT_OK(newYorkZone.outputDateWithFormat(os,
+                                               "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+                                               "dayOfWeek: %w, week: %U, isoYear: %G, "
+                                               "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+                                               date));
     ASSERT_EQ(os.str(),
               "1969/12/30 08:42:23:211, dayOfYear: 364, dayOfWeek: 3, week: 52, isoYear: 1970, "
               "isoWeek: 01, isoDayOfWeek: 2, percent: %");
@@ -568,12 +577,16 @@ TEST(NewYorkTimeAtEpoch, DoesComputeISOWeek) {
 TEST(UTCTimeAtEpoch, DoesFormatDate) {
     // Thu, Jan 1, 1970 00:00:00:000
     auto date = Date_t::fromMillisSinceEpoch(0);
-    ASSERT_EQ(TimeZoneDatabase::utcZone().formatDate("%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                                     date),
-              "1970/01/01 00:00:00:000, dayOfYear: 001, dayOfWeek: 5, week: 00, isoYear: 1970, "
-              "isoWeek: 01, isoDayOfWeek: 4, percent: %");
+    auto result = TimeZoneDatabase::utcZone().formatDate(
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date);
+    ASSERT_OK(result);
+    ASSERT_EQ(
+        "1970/01/01 00:00:00:000, dayOfYear: 001, dayOfWeek: 5, week: 00, isoYear: 1970, "
+        "isoWeek: 01, isoDayOfWeek: 4, percent: %",
+        result.getValue());
 }
 
 TEST(NewYorkTimeAtEpoch, DoesFormatDate) {
@@ -581,22 +594,27 @@ TEST(NewYorkTimeAtEpoch, DoesFormatDate) {
 
     // Thu, Jan 1, 1970 00:00:00:000Z
     auto date = Date_t::fromMillisSinceEpoch(0);
-    ASSERT_EQ(newYorkZone.formatDate("%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                     date),
-              "1969/12/31 19:00:00:000, dayOfYear: 365, dayOfWeek: 4, week: 52, isoYear: 1970, "
-              "isoWeek: 01, isoDayOfWeek: 3, percent: %");
+    auto result = newYorkZone.formatDate(
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date);
+    ASSERT_OK(result);
+    ASSERT_EQ(
+        "1969/12/31 19:00:00:000, dayOfYear: 365, dayOfWeek: 4, week: 52, isoYear: 1970, "
+        "isoWeek: 01, isoDayOfWeek: 3, percent: %",
+        result.getValue());
 }
 
 TEST(UTCTimeAtEpoch, DoesOutputFormatDate) {
     auto date = Date_t::fromMillisSinceEpoch(0);
     std::ostringstream os;
-    TimeZoneDatabase::utcZone().outputDateWithFormat(os,
-                                                     "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                                     date);
+    ASSERT_OK(TimeZoneDatabase::utcZone().outputDateWithFormat(
+        os,
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date));
     ASSERT_EQ(os.str(),
               "1970/01/01 00:00:00:000, dayOfYear: 001, dayOfWeek: 5, week: 00, isoYear: 1970, "
               "isoWeek: 01, isoDayOfWeek: 4, percent: %");
@@ -606,11 +624,11 @@ TEST(NewYorkTimeAtEpoch, DoesOutputFormatDate) {
     auto newYorkZone = kDefaultTimeZoneDatabase.getTimeZone("America/New_York");
     auto date = Date_t::fromMillisSinceEpoch(0);
     std::ostringstream os;
-    newYorkZone.outputDateWithFormat(os,
-                                     "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                     date);
+    ASSERT_OK(newYorkZone.outputDateWithFormat(os,
+                                               "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+                                               "dayOfWeek: %w, week: %U, isoYear: %G, "
+                                               "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+                                               date));
     ASSERT_EQ(os.str(),
               "1969/12/31 19:00:00:000, dayOfYear: 365, dayOfWeek: 4, week: 52, isoYear: 1970, "
               "isoWeek: 01, isoDayOfWeek: 3, percent: %");
@@ -880,47 +898,60 @@ TEST(NewYorkTimeAfterEpoch, DoesComputeISOWeek) {
 TEST(UTCTimeAfterEpoch, DoesFormatDate) {
     // Tue, Jun 6, 2017 19:38:43:234.
     auto date = Date_t::fromMillisSinceEpoch(1496777923234LL);
-    ASSERT_EQ(TimeZoneDatabase::utcZone().formatDate("%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                                     date),
-              "2017/06/06 19:38:43:234, dayOfYear: 157, dayOfWeek: 3, week: 23, isoYear: 2017, "
-              "isoWeek: 23, isoDayOfWeek: 2, percent: %");
+    auto result = TimeZoneDatabase::utcZone().formatDate(
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date);
+    ASSERT_OK(result);
+    ASSERT_EQ(
+        "2017/06/06 19:38:43:234, dayOfYear: 157, dayOfWeek: 3, week: 23, isoYear: 2017, "
+        "isoWeek: 23, isoDayOfWeek: 2, percent: %",
+        result.getValue());
 }
 
 TEST(NewYorkTimeAfterEpoch, DoesFormatDate) {
     // 2017-06-06T19:38:43:234Z (Tuesday).
     auto date = Date_t::fromMillisSinceEpoch(1496777923234LL);
     auto newYorkZone = kDefaultTimeZoneDatabase.getTimeZone("America/New_York");
-    ASSERT_EQ(newYorkZone.formatDate("%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                     date),
-              "2017/06/06 15:38:43:234, dayOfYear: 157, dayOfWeek: 3, week: 23, isoYear: 2017, "
-              "isoWeek: 23, isoDayOfWeek: 2, percent: %");
+    auto result = newYorkZone.formatDate(
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date);
+    ASSERT_OK(result);
+    ASSERT_EQ(
+        "2017/06/06 15:38:43:234, dayOfYear: 157, dayOfWeek: 3, week: 23, isoYear: 2017, "
+        "isoWeek: 23, isoDayOfWeek: 2, percent: %",
+        result.getValue());
 }
 
 TEST(UTCOffsetAfterEpoch, DoesFormatDate) {
     // 2017-06-06T19:38:43:234Z (Tuesday).
     auto date = Date_t::fromMillisSinceEpoch(1496777923234LL);
     auto offsetSpec = kDefaultTimeZoneDatabase.getTimeZone("+02:30");
-    ASSERT_EQ(offsetSpec.formatDate("%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                    "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                    "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                    date),
-              "2017/06/06 22:08:43:234, dayOfYear: 157, dayOfWeek: 3, week: 23, isoYear: 2017, "
-              "isoWeek: 23, isoDayOfWeek: 2, percent: %");
+    auto result = offsetSpec.formatDate(
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date);
+    ASSERT_OK(result);
+    ASSERT_EQ(
+        "2017/06/06 22:08:43:234, dayOfYear: 157, dayOfWeek: 3, week: 23, isoYear: 2017, "
+        "isoWeek: 23, isoDayOfWeek: 2, percent: %",
+        result.getValue());
 }
 
 TEST(UTCTimeAfterEpoch, DoesOutputFormatDate) {
     // Tue, Jun 6, 2017 19:38:43:234.
     auto date = Date_t::fromMillisSinceEpoch(1496777923234LL);
     std::ostringstream os;
-    TimeZoneDatabase::utcZone().outputDateWithFormat(os,
-                                                     "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                                     date);
+    ASSERT_OK(TimeZoneDatabase::utcZone().outputDateWithFormat(
+        os,
+        "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+        "dayOfWeek: %w, week: %U, isoYear: %G, "
+        "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+        date));
     ASSERT_EQ(os.str(),
               "2017/06/06 19:38:43:234, dayOfYear: 157, dayOfWeek: 3, week: 23, isoYear: 2017, "
               "isoWeek: 23, isoDayOfWeek: 2, percent: %");
@@ -931,11 +962,11 @@ TEST(NewYorkTimeAfterEpoch, DoesOutputFormatDate) {
     auto date = Date_t::fromMillisSinceEpoch(1496777923234LL);
     std::ostringstream os;
     auto newYorkZone = kDefaultTimeZoneDatabase.getTimeZone("America/New_York");
-    newYorkZone.outputDateWithFormat(os,
-                                     "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
-                                     "dayOfWeek: %w, week: %U, isoYear: %G, "
-                                     "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
-                                     date);
+    ASSERT_OK(newYorkZone.outputDateWithFormat(os,
+                                               "%Y/%m/%d %H:%M:%S:%L, dayOfYear: %j, "
+                                               "dayOfWeek: %w, week: %U, isoYear: %G, "
+                                               "isoWeek: %V, isoDayOfWeek: %u, percent: %%",
+                                               date));
     ASSERT_EQ(os.str(),
               "2017/06/06 15:38:43:234, dayOfYear: 157, dayOfWeek: 3, week: 23, isoYear: 2017, "
               "isoWeek: 23, isoDayOfWeek: 2, percent: %");
@@ -966,37 +997,42 @@ TEST(DateFormat, ThrowsUserExceptionIfGivenUnmatchedPercent) {
                        18535);
 }
 
-TEST(DateFormat, ThrowsUserExceptionIfGivenDateBeforeYear0) {
+TEST(DateFormat, ProducesNonOKStatusGivenDateBeforeYear0) {
     const long long kMillisPerYear = 31556926000;
 
-    ASSERT_THROWS_CODE(TimeZoneDatabase::utcZone().formatDate(
-                           "%Y", Date_t::fromMillisSinceEpoch(-(kMillisPerYear * 1971))),
-                       AssertionException,
-                       18537);
+    ASSERT_EQ(18537,
+              TimeZoneDatabase::utcZone()
+                  .formatDate("%Y", Date_t::fromMillisSinceEpoch(-(kMillisPerYear * 1971)))
+                  .getStatus()
+                  .code());
 
-    ASSERT_THROWS_CODE(TimeZoneDatabase::utcZone().formatDate(
-                           "%G", Date_t::fromMillisSinceEpoch(-(kMillisPerYear * 1971))),
-                       AssertionException,
-                       18537);
+    ASSERT_EQ(18537,
+              TimeZoneDatabase::utcZone()
+                  .formatDate("%G", Date_t::fromMillisSinceEpoch(-(kMillisPerYear * 1971)))
+                  .getStatus()
+                  .code());
 
-    ASSERT_EQ("0000",
-              TimeZoneDatabase::utcZone().formatDate(
-                  "%Y", Date_t::fromMillisSinceEpoch(-(kMillisPerYear * 1970))));
+    auto result = TimeZoneDatabase::utcZone().formatDate(
+        "%Y", Date_t::fromMillisSinceEpoch(-(kMillisPerYear * 1970)));
+    ASSERT_OK(result);
+    ASSERT_EQ("0000", result.getValue());
 }
 
-TEST(DateFormat, ThrowsUserExceptionIfGivenDateAfterYear9999) {
-    ASSERT_THROWS_CODE(
-        TimeZoneDatabase::utcZone().formatDate("%Y", Date_t::max()), AssertionException, 18537);
+TEST(DateFormat, ProducesNonOKStatusIfGivenDateAfterYear9999) {
+    ASSERT_EQ(18537,
+              TimeZoneDatabase::utcZone().formatDate("%Y", Date_t::max()).getStatus().code());
 
-    ASSERT_THROWS_CODE(
-        TimeZoneDatabase::utcZone().formatDate("%G", Date_t::max()), AssertionException, 18537);
+    ASSERT_EQ(18537,
+              TimeZoneDatabase::utcZone().formatDate("%G", Date_t::max()).getStatus().code());
 }
 
 TEST(DateFromString, CorrectlyParsesStringThatMatchesFormat) {
     auto input = "2017-07-04T10:56:02Z";
     auto format = "%Y-%m-%dT%H:%M:%SZ"_sd;
     auto date = kDefaultTimeZoneDatabase.fromString(input, kDefaultTimeZone, format);
-    ASSERT_EQ(TimeZoneDatabase::utcZone().formatDate(format, date), input);
+    auto result = TimeZoneDatabase::utcZone().formatDate(format, date);
+    ASSERT_OK(result);
+    ASSERT_EQ(input, result.getValue());
 }
 
 TEST(DateFromString, RejectsStringWithInvalidYearFormat) {