Add a note on the sign of daylight-saving offsets

Given that at least one zone has a negative offset (so that it's in
standard time for most of the year, including summer, and
daylight-saving time relatively briefly during winter), QTimeZone's
docs should explain what that means.

Change-Id: I6649b4cdefbd685dc97bf85d957960da44d07aed
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/corelib/time/qtimezone.cpp b/src/corelib/time/qtimezone.cpp
index 1f041c14fb..57ddef4e2d 100644
--- a/src/corelib/time/qtimezone.cpp
+++ b/src/corelib/time/qtimezone.cpp
@@ -209,7 +209,10 @@ Q_GLOBAL_STATIC(QTimeZoneSingleton, global_tz);
     standard time in the time zone.  The daylight-saving time offset is the
     number of seconds to add to the standard time offset to obtain
     daylight-saving time (abbreviated DST and sometimes called "daylight time"
-    or "summer time") in the time zone.
+    or "summer time") in the time zone. The usual case for DST (using
+    standard time in winter, DST in summer) has a positive daylight-saving
+    time offset. However, some zones have negative DST offsets, used in
+    winter, with summer using standard time.
 
     Note that the standard and DST offsets for a time zone may change over time
     as countries have changed DST laws or even their standard time offset.