RESOLVED FIXED Bug 137458
[Win] DateMath's calculateUTCOffset does not account for Daylight Savings Time 
https://bugs.webkit.org/show_bug.cgi?id=137458
Summary [Win] DateMath's calculateUTCOffset does not account for Daylight Savings Time
Brent Fulgham
Reported 2014-10-06 13:23:07 PDT
The code for the Windows path of "calculateUTCOffset" ignores the return value of GetTimeZoneInformation, and always acts as though the running machine is in the standard time zone. This documentation in <http://msdn.microsoft.com/en-us/library/windows/desktop/ms724421(v=vs.85).aspx> clearly indicates a daylight-savings-time-specific return value that indicates that you should use the "daylight bias" portion of the time zone struct to calculate the correct offset.
Attachments
Patch (2.57 KB, patch)
2014-10-06 13:30 PDT, Brent Fulgham 		no flags
DetailsFormatted DiffDiff
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Radar WebKit Bug Importer
Comment 1 2014-10-06 13:24:12 PDT
<rdar://problem/18559172>
Brent Fulgham
Comment 2 2014-10-06 13:30:43 PDT
Created attachment 239351 [details] Patch
Brent Fulgham
Comment 3 2014-10-06 13:31:11 PDT
This bug may be why certain date-related tests are failing depending on user's time zone.
Geoffrey Garen
Comment 4 2014-10-06 13:34:35 PDT
Comment on attachment 239351 [details] Patch r=me It would be nice to get clarity on whether our existing tests cover this, and to add a test to cover this if it's not already covered.
Brent Fulgham
Comment 5 2014-10-06 17:39:35 PDT
(In reply to comment #4) > (From update of attachment 239351 [details]) > r=me > > It would be nice to get clarity on whether our existing tests cover this, and to add a test to cover this if it's not already covered. We have tests that check for correct calculation of DST-related dates, but we don't have a test that places the test machine in DST or Standard time zones for running the tests. This patch corrects a problem where the local machine state was not being accounted for when computed the time offset compared to UTC. I'll think about this and see if we can come up with a reliable way to toggle this state during test runs.
Brent Fulgham
Comment 6 2014-10-06 17:42:19 PDT
See also <https://bugs.webkit.org/show_bug.cgi?id=137473> for better testing for this feature.
WebKit Commit Bot
Comment 7 2014-10-06 18:15:22 PDT
Comment on attachment 239351 [details] Patch Clearing flags on attachment: 239351 Committed r174377: <http://trac.webkit.org/changeset/174377>
WebKit Commit Bot
Comment 8 2014-10-06 18:15:26 PDT
All reviewed patches have been landed. Closing bug.
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