That is a specific problem with the third-party library `pytz`, not a standard feature of the datetime module. Using `datetime.replace` is the intended way to set a time zone, see: https://blog.ganssle.io/articles/2018/03/pytz-fastest-footgun.html

As of Python 3.6, we've been recommending dateutil.tz instead of pytz, and assuming PEP 615 is accepted ( https://www.python.org/dev/peps/pep-0615/ ), we will have a built in time zone type that supports IANA time zones.

I am going to close this because this is not a bug in CPython, but if you think otherwise feel free to continue using this ticket to make the case.