SERVER-29284 Add support for UTC offsets to $dateFromString

2 files changed, 28 insertions, 22 deletions

diff --git a/src/mongo/db/query/datetime/date_time_support.cpp b/src/mongo/db/query/datetime/date_time_support.cpp
index 1ab22b6bc09..c7719014d9d 100644
--- a/src/mongo/db/query/datetime/date_time_support.cpp
+++ b/src/mongo/db/query/datetime/date_time_support.cpp
@@ -219,15 +219,9 @@ Date_t TimeZoneDatabase::fromString(StringData dateString, boost::optional<TimeZ
                           "at the same time");
                 break;
         }
-
-        // _tzInfo, although private, can be accessed because TimeZoneDatabase is a friend of
-        // TimeZone.
-        timelib_update_ts(parsedTime.get(), tz->_tzInfo.get());
-    } else {
-        timelib_update_ts(parsedTime.get(), nullptr);
     }
 
-    timelib_unixtime2local(parsedTime.get(), parsedTime->sse);
+    tz->adjustTimeZone(parsedTime.get());
 
     return Date_t::fromMillisSinceEpoch(
         durationCount<Milliseconds>(Seconds(parsedTime->sse) + Microseconds(parsedTime->us)));
@@ -288,14 +282,14 @@ TimeZone TimeZoneDatabase::getTimeZone(StringData timeZoneId) const {
               str::stream() << "unrecognized time zone identifier: \"" << timeZoneId << "\"");
 }
 
-void TimeZone::adjustTimeZone(timelib_time* t) const {
-    if (_tzInfo) {
-        timelib_set_timezone(t, _tzInfo.get());
-    } else if (durationCount<Seconds>(_utcOffset)) {
-        timelib_set_timezone_from_offset(t, -durationCount<Seconds>(_utcOffset));
+void TimeZone::adjustTimeZone(timelib_time* timelibTime) const {
+    if (isTimeZoneIDZone()) {
+        timelib_set_timezone(timelibTime, _tzInfo.get());
+    } else if (isUtcOffsetZone()) {
+        timelib_set_timezone_from_offset(timelibTime, -durationCount<Seconds>(_utcOffset));
     }
-    timelib_update_ts(t, nullptr);
-    timelib_update_from_sse(t);
+    timelib_update_ts(timelibTime, nullptr);
+    timelib_update_from_sse(timelibTime);
 }
 
 Date_t TimeZone::createFromDateParts(
diff --git a/src/mongo/db/query/datetime/date_time_support.h b/src/mongo/db/query/datetime/date_time_support.h
index 9c85a3d6f6c..ddfd32853bc 100644
--- a/src/mongo/db/query/datetime/date_time_support.h
+++ b/src/mongo/db/query/datetime/date_time_support.h
@@ -49,7 +49,6 @@ namespace mongo {
  * for the hour, minute, or second of a date, even when given the same date.
  */
 class TimeZone {
-    friend class TimeZoneDatabase;
 
 public:
     /**
@@ -130,7 +129,21 @@ public:
      * Returns whether this is the zone representing UTC.
      */
     bool isUtcZone() const {
-        return _tzInfo == nullptr;
+        return (_tzInfo == nullptr && !durationCount<Seconds>(_utcOffset));
+    }
+
+    /**
+     * Returns whether this is a zone representing a UTC offset, like "+04:00".
+     */
+    bool isUtcOffsetZone() const {
+        return durationCount<Seconds>(_utcOffset) != 0;
+    }
+
+    /**
+     * Returns whether this is a zone representing an Olson time zone, like "Europe/London".
+     */
+    bool isTimeZoneIDZone() const {
+        return _tzInfo != nullptr;
     }
 
     /**
@@ -166,6 +179,11 @@ public:
     Seconds utcOffset(Date_t) const;
 
     /**
+     * Adjusts 'timelibTime' according to this time zone definition.
+     */
+    void adjustTimeZone(timelib_time* timelibTime) const;
+
+    /**
      * 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
@@ -297,12 +315,6 @@ private:
         void operator()(timelib_tzinfo* tzInfo);
     };
 
-    /**
-     * Helper function to apply tzInfo and utcOffset information to the constructed timelib_time*
-     * value.
-     */
-    void adjustTimeZone(timelib_time* t) const;
-
     // null if this TimeZone represents the default UTC time zone, or a UTC-offset time zone
     std::shared_ptr<timelib_tzinfo> _tzInfo;