> libc = ctypes.cdll.msvcrt

That's the private CRT of Windows, not the Universal CRT for applications. In a release build (python.exe), use ctypes.CDLL('ucrtbase', use_errno=True). In a debug build (python_d.exe), use ctypes.CDLL('ucrtbased', use_errno=True).

I suppose we should use API sets [1] for the release build, such as "api-ms-win-crt-locale-l1-1-0" and 
"api-ms-win-crt-time-l1-1-0". But they resolve to "ucrtbase". 

[1]: https://docs.microsoft.com/en-us/uwp/win32-and-com/win32-extension-apis