[Android] Filter UTC aliases from GetSystemTimeZones to avoid duplicate display names

[Copilot]

TimeZoneInfoTests.TestGetSystemTimeZones fails on Android because GetSystemTimeZones() returns UTC aliases (UCT, Etc/UTC, Zulu, etc.) alongside UTC, all sharing the same display name "(UTC) Coordinated Universal Time".

Changes

• Skip UTC aliases in PopulateAllSystemTimeZones using existing IsUtcAlias() check
• UTC itself is explicitly added to the dictionary before the loop, so it remains in the list

foreach (string timeZoneId in GetTimeZoneIds())
{
    // Skip UTC aliases to avoid duplicate display names in the list.
    // UTC is already added to the dictionary at the start.
    if (IsUtcAlias(timeZoneId))
    {
        continue;
    }
    // ... rest of population logic
}

Fixes #121963

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[android] System.Tests.TimeZoneInfoTests.TestGetSystemTimeZones failure: Assert.DoesNotContain</issue_title>
<issue_description>## Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1211662
Build error leg or test failing: System.Tests.TimeZoneInfoTests.TestGetSystemTimeZones
Pull request: #121824

[FAIL] System.Tests.TimeZoneInfoTests.TestGetSystemTimeZones
Assert.DoesNotContain() Failure: Filter matched in collection
                                                                                      ↓ (pos 242)
Collection: [···, (UTC) Coordinated Universal Time, (UTC) Coordinated Universal Time, (UTC) Coordinated Universal Time, (UTC) Coordinated Universal Time, (UTC) Coordinated Universal Time, ···]
   at System.Tests.TimeZoneInfoTests.TestGetSystemTimeZones()
   at System.RuntimeMethodHandle.InvokeMethod(ObjectHandleOnStack target, Void** arguments, ObjectHandleOnStack sig, BOOL isConstructor, ObjectHandleOnStack result)
   at System.RuntimeMethodHandle.InvokeMethod(ObjectHandleOnStack target, Void** arguments, ObjectHandleOnStack sig, BOOL isConstructor, ObjectHandleOnStack result)
   at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)

Error Message

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": ["[FAIL] System.Tests.TimeZoneInfoTests.TestGetSystemTimeZones", "Assert.DoesNotContain() Failure: Filter matched in collection"],
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1211662
Error message validated: [[FAIL] System.Tests.TimeZoneInfoTests.TestGetSystemTimeZones Assert.DoesNotContain() Failure: Filter matched in collection]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 11/25/2025 5:11:04 PM UTC

Comments on the Issue (you are @copilot in this section)

• Fixes [android] System.Tests.TimeZoneInfoTests.TestGetSystemTimeZones failure: Assert.DoesNotContain #121963

---

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[am11]

IsUtcAlias can also be simplified:

private static bool IsUtcAlias(string id) => id[0] switch
{
    'e' or 'E' => string.Equals(id, "Etc/UTC", StringComparison.OrdinalIgnoreCase) ||
                  string.Equals(id, "Etc/UCT", StringComparison.OrdinalIgnoreCase) ||
                  string.Equals(id, "Etc/Universal", StringComparison.OrdinalIgnoreCase) ||
                  string.Equals(id, "Etc/Zulu", StringComparison.OrdinalIgnoreCase),
    'u' or 'U' => string.Equals(id, "UCT", StringComparison.OrdinalIgnoreCase) ||
                  string.Equals(id, "UTC", StringComparison.OrdinalIgnoreCase) ||
                  string.Equals(id, "Universal", StringComparison.OrdinalIgnoreCase),
    'z' or 'Z' => string.Equals(id, "Zulu", StringComparison.OrdinalIgnoreCase),
    _ => false
};

[am11]

Fixes #121882

It is unrelated?

[simonrozsival]

It is unrelated?

Yes, copilot got it wrong. Edited.

[tarekgh]

I don't think this is the right fix. We have the issue #90269 tracking ensuring not returning any duplicates on Android. When this issue get fixed should include UTC alias duplicate too. The change in this PR will add extra overhead for other platforms which is not necessary. I would say disable the failing test on Android for now.

CC @davidnguyen-tech @matouskozak

[dotnet-policy-service]

Tagging subscribers to 'arch-android': @vitek-karas, @simonrozsival, @steveisok, @akoeplinger
See info in area-owners.md if you want to be subscribed.

[tarekgh]

@simonrozsival could you please ensure disabling the failing test for Android platform then close #121963 to avoid skipping failures on other platforms? Thanks!

[simonrozsival]

@tarekgh yes, I will disable the test tomorrow