Three years ago Paul Ganssle wrote a comparison about time zone handling between
python-dateutil. In this article he shows how it's easy to use
pytz in an incorrect way that is hard to spot because it's almost correct:
In Home Assistant 2021.6 we're going to switch to
python-dateutil. You will need to upgrade your custom integration if it relies on the unofficial interface
my_time_zone.localize(my_dt). Use Python's official method
hass.config.time_zone will also change to a string instead of a time zone object.
Thanks to @bdraco for helping revive this effort and push this change past the finish line. We actually found a couple of bugs during the migration! Also thanks to Paul Ganssle for maintaining
python-dateutil and the excellent write up.
Wow, time flies! Paul, the author of
python-dateutil and also the author of the blog post that inspired us, pointed us to the fact that Python 3.9 includes upgraded timezone handling and that we should use that instead. With the help of Nick and Paul
python-dateutil has been removed again and
zoneinfo is used instead (PR).