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fix: improper use of ucal_inDaylightTime#6097
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`ucal_inDaylightTime` is used to check whether the timezone is currently observing DST. STL (likely in an attempt to be defensive) tries to use it as a way to tell whether the timezone observed DST on the date in question (which could be in the past), which is wrong.
StephanTLavavej
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Feb 22, 2026
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StephanTLavavej
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Feb 22, 2026
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Added regression tests for timezones that abolished DST to ensure correct historical offsets.
StephanTLavavej
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Feb 22, 2026
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Thanks! I've manually verified that the regression test produced all wrong answers before the fix. |
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I'm mirroring this to the MSVC-internal repo. Please notify me if any further changes are pushed, otherwise no action is required. |
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ucal_inDaylightTimeis used to check whether the timezone is currently observing DST. STL (likely in an attempt to be defensive) tries to use it as a way to tell whether the timezone observed DST on the date in question (which could be in the past), which is wrong.Fixing that by omitting use of that guard before obtaining DST offset.
fixes: #6096