I am not sure this is a bug, as I don't think it reasonable to expect every time function call to re-initialize the timezone setting. I think you should change this to a request to see if time.tzset can now be made to work on Windows and not unix-only (as documented, when added in 2.3). The second StackOverflow answer by Lentjes suggests that it can for current Python.

datetime.now(tz=None) has an option to pass a timezone for adjusting the output. An user-friendly app can pass a real timezone instead of the default None and give users means to change what tz they want times displayed for, which may or may not be the current local timezone.