What's the difference between pytz and python-dateutil?

This article gives a nice overview of the differences between the two libraries, with the biggest difference apparently being the correctness of DST edge cases (where dateutil.tz has advantage).

They both provide useful support for dealing with timezones. I've personally used pytz in my django applications and found it useful and easy to work with. Hope my two cents helps.

I use both packages. I don't personally like the way python-dateutil is packaged (the whole this version of python 2 and this version for python 3), it used to not even be on pypi. python-dateutil is great for parsing, even if it is somewhat slow (it is parsing though). I'd bet my money on the pytz package becoming the standard for timezones.