macos - How should I fetch TimeZoneInfo in a platform-agnostic way?

Question

I'm working on porting a .NET Framework 4.5 app to .NET Core 2.0 and have started to do some testing on my Mac. When I run this code on .NET Core 2.0 on Windows it works fine:

TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time");

but it throws the following exception on the Mac:

System.TimeZoneNotFoundException: The time zone ID 'Pacific Standard Time' was not found on the local computer. ---> System.IO.FileNotFoundException: Could not find file '/usr/share/zoneinfo/Pacific Standard Time'.
   at Interop.ThrowExceptionForIoErrno(ErrorInfo errorInfo, String path, Boolean isDirectory, Func`2 errorRewriter)
   at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String path, OpenFlags flags, Int32 mode)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
   at System.IO.File.ReadAllBytes(String path)
   at System.TimeZoneInfo.TryGetTimeZoneFromLocalMachine(String id, TimeZoneInfo& value, Exception& e)
   --- End of inner exception stack trace ---
   at System.TimeZoneInfo.FindSystemTimeZoneById(String id)

After some poking around, it seems that using the time zone ID "America/Los_Angeles" fixes the problem on the Mac.

I'm wondering what I should do to keep this platform agnostic. Should I try to find "Pacific Standard Time", and then try to find "America/Los Angeles" in a catch block? That seems clumsy, and what if another platform has yet another string for it? Is there a better way to look up the TimeZoneInfo I want?

Answer 1

This is a known problem, and is tracked in dotnet/corefx#11897. There's no built-in solution yet.

However, my TimeZoneConverter library can be used for this.

TimeZoneInfo tzi = TZConvert.GetTimeZoneInfo("Pacific Standard Time");

It works by first seeing if the time zone is present on the computer. If not, then it converts to the equivalent time zone in IANA format (America/Los_Angeles in this case), and trying to retrieve it with that instead. The opposite case also works, so you can use either format on any OS.