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pythondjangotimezonedst

Resolving AmbiguousTimeError from Django's make_aware

I have a code as follows:

from django.utils.timezone import get_current_timezone, make_aware

make_aware(some_datetime, get_current_timezone())

The make_aware call occasionally raises

AmbiguousTimeError: 2013-11-03 01:23:17

I know from the Django docs that this is a daylight savings problem, and that this timestamp is in fact ambiguous. Now how do i resolve it (say to the first of the two possible times this could be)?

Solution

  • Prophylactics

    You should avoid naive datetimes in the first place using the following:

    from django.utils import timezone
now = timezone.now()

    If like me, you have naive times already that you must convert, read on!

    Django 4+:

    Starting in Django 4, if you use zoneinfo for timezone support (which is the default in Django 4) there's nothing you need to do to use make_aware to avoid this error. The is_dst flag to make_aware is deprecated in Django 4 and will be removed in Django 5.

    Django 1.9 - 3.2:

    You can resolve the AmbiguousTimeError by using the following (thanks to GeyseR):

    from django.utils import timezone

# This uses `settings.TIME_ZONE` unless you call `timezone.activate()`
timezone.make_aware(some_datetime, is_dst=False)

    Django 1.x - 1.8:

    The problem is that make_aware just calls timezone.localize, passing None to the argument is_dst:

    timezone.localize(value, is_dst=None)

    The argument is_dst is specifically what is used to resolve this ambiguous time error (http://pytz.sourceforge.net/#tzinfo-api).

    The solution is to call timezone.localize yourself:

    get_current_timezone().localize(some_datetime, is_dst=False)

    Having is_dst=False sets it to the first of the two possible times. is_dst=True would be the second.