Closed
Description
Description
It looks like the TimeZoneInfo object that is returned from FindSystemTimeZoneById() is returning an incorrect name for a given ID (It gives the correct offset but with "GMT"). Further, it seems to only be a problem for IDs that are shaped like "Eastern Standard Time". In contrast, "America/New_York" works fine.
I suspect that this has something to do with the caching behavior introduced in .NET 8. Take a look at the unit test below, which will fail in different ways depending on the test cases provided
Unit test to reproduce behavior:
public class TimeZoneHelperTests
{
[Theory]
[InlineData("Eastern Standard Time", false, "EST")] // fully qualified IDs fail sometimes
[InlineData("Central Standard Time", false, "CST")]
[InlineData("Mountain Standard Time", false, "MST")]
[InlineData("Pacific Standard Time", false, "PST")]
[InlineData("Eastern Standard Time", true, "EDT")]
[InlineData("Central Standard Time", true, "CDT")]
[InlineData("Mountain Standard Time", true, "MDT")]
[InlineData("Pacific Standard Time", true, "PDT")]
[InlineData("America/New_York", false, "EST")] //America/X type IDs always succeed
[InlineData("America/Chicago", false, "CST")]
[InlineData("America/Denver", false, "MST")]
[InlineData("America/Los_Angeles", false, "PST")]
[InlineData("America/New_York", true, "EDT")]
[InlineData("America/Chicago", true, "CDT")]
[InlineData("America/Denver", true, "MDT")]
[InlineData("America/Los_Angeles", true, "PDT")]
public void GetTzAbbreviation_BuildsCorrectAbbreviation(string timeZoneId, bool isDaylightSavingsTime, string expectedAbbreviation)
{
// Arrange
var tzi = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId);
// Act
var abbreviation = GetTzAbbreviation(isDaylightSavingsTime, tzi);
// Assert
Assert.Equal(expectedAbbreviation, abbreviation);
}
private static string GetTzAbbreviation(bool isDaylightSavingsTime, TimeZoneInfo timeZoneInfo)
{
var timeZoneString = isDaylightSavingsTime ? timeZoneInfo.DaylightName : timeZoneInfo.StandardName;
return string.Concat(Regex
.Matches(timeZoneString, "[A-Z]")
.Select(match => match.Value));
}
}Version
.NET 8 GA
Previous behavior
The standard name should be analogous the provided time zone.
New behavior
The standard name is set to GMT
Type of breaking change
- Binary incompatible: Existing binaries might encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
- Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code might require source changes to compile successfully.
- Behavioral change: Existing binaries might behave differently at run time.
Reason for change
N/A
Recommended action
Seems like the America/X IDs are working properly. Use those instead
Feature area
Core .NET libraries