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[Android] Filter UTC aliases from GetSystemTimeZones to avoid duplicate display names #121964

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[Android] Filter UTC aliases from GetSystemTimeZones to avoid duplicate display names #121964

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Copilot Nov 25, 2025
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Filter UTC aliases from GetSystemTimeZones to avoid duplicate display…
Copilot Nov 25, 2025
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8 changes: 8 additions & 0 deletions src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.Unix.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -308,6 +308,14 @@ private static Dictionary<string, TimeZoneInfo> PopulateAllSystemTimeZones(Cache

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, and aliases like
// UCT, Etc/UTC, Zulu, etc. have the same display name as UTC.
if (IsUtcAlias(timeZoneId))
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@am11 am11 Nov 25, 2025

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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
};

{
continue;
}

if (TryGetTimeZone(timeZoneId, false, out TimeZoneInfo? timeZone, out _, cachedData, alwaysFallbackToLocalMachine: true) == TimeZoneInfoResult.Success &&
timeZone is not null)
{
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