runtime: .NET 6 TimeZoneInfo.FindSystemTimeZoneById does not support IANA timezone ids on Windows Server 2016 & 2019

Description

As announced here: https://devblogs.microsoft.com/dotnet/date-time-and-time-zone-enhancements-in-net-6/ starting with .NET 6 TimeZoneInfo.FindSystemTimeZoneById should now support IANA timezone ids. That works just fine on Windows 10/10 & Windows Server 2022. It does not work on Windows Server 2016 & 2019 thought. Those are versions user by Azure App Services today. So, this functionality simple does not work on Azure.

Reproduction Steps

System.Console.WriteLine(“{0}”, System.TimeZoneInfo.FindSystemTimeZoneById(“Europe/Copenhagen”).Id);

Expected behavior

IANA timezone is resolved no matter what OS the code is run on.

Actual behavior

It is not resolved.

Regression?

Technically, it’s not a regression. But, TimeZoneConverter library which was recommended to use before seems to be struggling to find a new maintainer: https://github.com/mattjohnsonpint/TimeZoneConverter/issues/105 which means it may not have regular updates in the future.

Known Workarounds

Add this to a project file helps:

<ItemGroup>
    <PackageReference Include="Microsoft.ICU.ICU4C.Runtime" Version="68.2.0.9" />
    <RuntimeHostConfigurationOption Include="System.Globalization.AppLocalIcu" Value="68.2" />
</ItemGroup>

This, however, has to be done to every single project which is tedious, time-consuming and error-prone. Moreover, if we have a test DLL which uses TimeZoneInfo.FindSystemTimeZoneById, this workaround does not work (it only applies to EXEs).

Configuration

No response

Other information

No response

About this issue

Original URL
State: closed
Created 3 years ago
Reactions: 1
Comments: 18 (10 by maintainers)

Most upvoted comments

I just hit this problem, too. I read the blog post announcing the new features in .NET 6, then happily removed references to TimeZoneConverter from my project because .NET supports it natively now! But when I pushed my changes, my units tests failed on GitHub Actions because IANA names do not work on Windows Server 2019. How do we apply the necessary “app-local ICU” configuration for unit tests?

wjrogers on Dec 3, 2021

The proposed solution does also work for unit tests. You just have to add the same properties/package to the test projects too.

martincostello on Dec 3, 2021

Reopen to try find a solution for the unit tests.

tarekgh on Dec 3, 2021