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Fix TimeZoneInfo to handle Yukon zone #43550

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Merged
merged 3 commits into from
Oct 18, 2020
Merged

Fix TimeZoneInfo to handle Yukon zone #43550

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0233a80
Fix TimeZoneInfo to handle Yukun zone
tarekgh Oct 17, 2020
553ac68
Address the feedback
tarekgh Oct 17, 2020
e92960c
Fix failing test
tarekgh Oct 18, 2020
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6 changes: 2 additions & 4 deletions src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.AdjustmentRule.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -119,8 +119,7 @@ internal static AdjustmentRule CreateAdjustmentRule(
internal bool IsStartDateMarkerForBeginningOfYear() =>
!NoDaylightTransitions &&
DaylightTransitionStart.Month == 1 && DaylightTransitionStart.Day == 1 &&
DaylightTransitionStart.TimeOfDay.TimeOfDay.Ticks < TimeSpan.TicksPerSecond && // < 12:00:01 AM
_dateStart.Year == _dateEnd.Year;
DaylightTransitionStart.TimeOfDay.TimeOfDay.Ticks < TimeSpan.TicksPerSecond; // < 12:00:01 AM

//
// When Windows sets the daylight transition end Jan 1st at 12:00 AM, it means the year ends with the daylight saving on.
Expand All @@ -129,8 +128,7 @@ internal bool IsStartDateMarkerForBeginningOfYear() =>
internal bool IsEndDateMarkerForEndOfYear() =>
!NoDaylightTransitions &&
DaylightTransitionEnd.Month == 1 && DaylightTransitionEnd.Day == 1 &&
DaylightTransitionEnd.TimeOfDay.TimeOfDay.Ticks < TimeSpan.TicksPerSecond && // < 12:00:01 AM
_dateStart.Year == _dateEnd.Year;
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@stephentoub stephentoub Oct 17, 2020 •
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Do you know why this extra check was there in the first place / what it was trying to prevent?

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@tarekgh tarekgh Oct 17, 2020

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It was done long ago to minimize the risk on the Full Framework and we didn't have any case breaking this. But now we got the case that broke it.

DaylightTransitionEnd.TimeOfDay.TimeOfDay.Ticks < TimeSpan.TicksPerSecond; // < 12:00:01 AM

/// <summary>
/// Helper function that performs all of the validation checks for the factory methods and deserialization callback.
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34 changes: 34 additions & 0 deletions src/libraries/System.Runtime/tests/System/TimeZoneInfoTests.cs
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Expand Up @@ -119,6 +119,40 @@ public static void LibyaTimeZone()
Assert.True(libyaLocalTime.Equals(expectResult), string.Format("Expected {0} and got {1}", expectResult, libyaLocalTime));
}

[ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsWindows))]
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@stephentoub stephentoub Oct 17, 2020

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Why does this need to be Windows specific? Wondering if it can be written in a way that works on Linux when running on an ICU that contains data for the same time zone.

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@tarekgh tarekgh Oct 17, 2020

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I restricted this to Windows only for multiple reasons, first Windows zone id Yukon Standard Time cannot be used on Linux. Second the rules on Linux is very different than Windows. I added this test case mainly to test Windows edge cases. As I mentioned Windows has some limitation which cannot specify more than one transition per year while Linux data don't have this restriction. I am not expecting Yukon on Linux would be any different than any other zone which we already testing.

public static void TestYukunTZ()
{
try
{
TimeZoneInfo yukon = TimeZoneInfo.FindSystemTimeZoneById("Yukon Standard Time");

// First, ensure we have the updated data
TimeZoneInfo.AdjustmentRule [] rules = yukon.GetAdjustmentRules();
if (rules.Length <= 0 || rules[rules.Length - 1].DateStart.Year != 2021 || rules[rules.Length - 1].DateEnd.Year != 9999)
{
return;
}

TimeSpan minus7HoursSpan = new TimeSpan(-7, 0, 0);

DateTimeOffset midnight = new DateTimeOffset(2021, 1, 1, 0, 0, 0, 0, minus7HoursSpan);
DateTimeOffset beforeMidnight = new DateTimeOffset(2020, 12, 31, 23, 59, 59, 999, minus7HoursSpan);
DateTimeOffset before1AM = new DateTimeOffset(2021, 1, 1, 0, 59, 59, 999, minus7HoursSpan);
DateTimeOffset at1AM = new DateTimeOffset(2021, 1, 1, 1, 0, 0, 0, minus7HoursSpan);
DateTimeOffset midnight2022 = new DateTimeOffset(2022, 1, 1, 0, 0, 0, 0, minus7HoursSpan);

Assert.Equal(minus7HoursSpan, yukon.GetUtcOffset(midnight));
Assert.Equal(minus7HoursSpan, yukon.GetUtcOffset(beforeMidnight));
Assert.Equal(minus7HoursSpan, yukon.GetUtcOffset(before1AM));
Assert.Equal(minus7HoursSpan, yukon.GetUtcOffset(at1AM));
Assert.Equal(minus7HoursSpan, yukon.GetUtcOffset(midnight2022));
}
catch (TimeZoneNotFoundException)
{
// Some Windows versions don't carry the complete TZ data. Ignore the tests on such versiosn.
}
}

[Fact]
public static void RussianTimeZone()
{
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