On OS 10.12, I set the language to Chinese Traditional Taiwan, the API CultureInfo.CurrentUICulture returns zh-HK.
While native Apple API NSLocale can return correct value as zh-Hant-TW
Do you have a simple way to test this? Would be nice to reproduce this in a testable manner?
I was able to test this by changing the language on the siulator and calling the specified APIS:
The same difference occurs for Traditional Chinese (Hong Kong), CurrentUICulture simply shows zh-HK same as traditional Taiwan (can't actually test taiwan as it doesn't appear to be an option in my simulator).
Whoops, just realized this was a mac bug and I tested on iOS. Tested on mac now (set machine to traditional chinese taiwan) and saw the same error there.
So looks like it affects both iOS and mac.
*** Bug 59415 has been marked as a duplicate of this bug. ***