pytz has served the Python community well for many years, but it is no longer
the best option for providing time zones. pytz has a non-standard interface
that is very easy to misuse; this interface was necessary when pytz was
created, because datetime had no way to represent ambiguous datetimes, but this
was solved in Python 3.6, which added a fold attribute to datetimes in PEP 495.
With the addition of the zoneinfo module in Python 3.9 (PEP 615), there has
never been a better time to migrate away from pytz.
However, since pytz time zones are used very differently from a standard
tzinfo, and many libraries have built pytz zones into their standard time zone
interface (and thus may have users relying on the existence of the localize and
normalize methods); this library provides shim classes that are compatible with
both PEP 495 and pytz’s interface, to make it easier for libraries to deprecate
pytz.
