Home/ Questions/Can't compare offset-naive and offset-aware datetimes - how can i circumvent the error?
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Mila Parent
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Asked: 2022-05-18T10:39:21+00:00 In:

Can’t compare offset-naive and offset-aware datetimes – how can i circumvent the error?

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I’m building a new program, but when I run it, an error pops up. The error displayed is as follows:

TypeError: can't compare offset-naive and offset-aware datetimes

I have tried several workarounds, but they still do not get the desired results. If you have come across this situation and have a solution for the “can’t compare offset-naive and offset-aware datetimes” problem, pls let me know. Here is what I do:

if challenge.datetime_start <= datetime.now() <= challenge.datetime_end:

class Fundraising_Challenge(models.Model):
  name = models.CharField(max_length=100)
  datetime_start = models.DateTimeField()
  datetime_end = models.DateTimeField()

Thanks!

compare offset-naive and offset-aware datetimes
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2 Answers

  1. Best Answer
    Expert

    The cause:

    This error happens due to both of datetime.datetime.now() and datetime.datetime.utcnow() are  unaware the time zones.

    Solution: 

    By default, naive is datetime object in Python, so it’s essential to make them aware of  datetime objects. You can do this by:

    import datetime
import pytz

utc=pytz.UTC

challenge.datetime_start = utc.localize(challenge.datetime_start) 
challenge.datetime_end = utc.localize(challenge.datetime_end) 
# now both the datetime objects are aware, so you can compare them

    An important thing you need to note is that if tzinfo has already been set, this would raise ValueError. You can use these following command to check:

    start_time = challenge.datetime_start.replace(tzinfo=utc)
end_time = challenge.datetime_end.replace(tzinfo=utc)

    A UNIX timestamp also could be formatted by using datetime.datetime object and timezone information as follows:

    d = datetime.datetime.utcfromtimestamp(int(unix_timestamp))
d_with_tz = datetime.datetime(
 year=d.year,
 month=d.month,
 day=d.day,
 hour=d.hour,
 minute=d.minute,
 second=d.second,
 tzinfo=pytz.UTC)
    • 11

  2. datetime.datetime.now does not recognize time zones.

    Django includes a helper to do this. This requires pytz 

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

    It should be possible to compare now and challenge.datetime_start

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