Are there any "correct" implementations of tzinfo?

[Random832]

I was trying to find out how arithmetic on aware datetimes is "supposed
to" work, and tested with pytz. When I posted asking why it behaves this
way I was told that pytz doesn't behave correctly according to the way
the API was designed. The tzlocal module, on the other hand, appears to
simply defer to pytz on Unix systems.

My question is, _are_ there any correct reference implementations that
demonstrate the proper behavior in the presence of a timezone that has
daylight saving time transitions?