NonExistentTimeError thrown during DST transition

[babus]

Here is my model field, I need to show all the obsolete timezones as the frontend clients still send the timezone in obsolete formats(Asia/Calcutta instead of Asia/Kokatta). Not sure if that's the reason.

TIMEZONE_CHOICES = [(pytz.timezone(tz), tz) for tz in pytz.all_timezones]

timezone = TimeZoneField(choices_display='WITH_GMT_OFFSET', choices=TIMEZONE_CHOICES, blank=True, null=True)

Error

timezone = TimeZoneField(choices_display='WITH_GMT_OFFSET', choices=TIMEZONE_CHOICES, blank=True, null=True)
  File "timezone_field/fields.py", line 72, in __init__
    choices = with_gmt_offset(values)
  File "timezone_field/choices.py", line 32, in with_gmt_offset
    delta = pytz.timezone(tz_str).utcoffset(now)
  File "pytz/tzinfo.py", line 422, in utcoffset
    dt = self.localize(dt, is_dst)
  File "pytz/tzinfo.py", line 341, in localize
    raise NonExistentTimeError(dt)

[mfogel]

Yeah, under the hood this field uses pytz to get metadata about timezones. If pytz doesn't recognize a string as a valid timezone, it will throw one of those NonExistentTimeError exceptions. So it looks like that's whats happening here: the obsolete timezones are not being recognized by pytz.

If you have to support the obsolete timezones, perhaps just a standard string field with a choices argument might suffice?

[babus]

@mfogel Thanks for responding! I think the problem isn't with the obsolete timezones even America/Adak is in pytz.common_timezones. I guess that it can be fixed with any one of the solutions put out here and also this exception from pytz is intentional. is_dst needs to be sent True or False based on the exceptions. Since this blocks the initialization of the models and so the gunicorn workers to crash when they restart, I think this needs to be prioritized. I'm sure that everyone who is using the library in production have had bunch of errors for like an hour in the reported time.

Thanks for the work!
/Babu

[mfogel]

Ahh, I see what's going on. Thanks @babu-upcomer for the link and more detailed explanation.

Yeah I think for anyone using this field and using the kwarg choices_display='WITH_GMT_OFFSET' they probably got this error during the recent north america DST transition.

It looks like Europe will be undergoing a DST transition in a few weeks, I will plan to get this bug fixed and an update pushed to pypi before then.

[mfogel]

Fix released as part of v4.1.2