267

I am trying to compare the current date and time with dates and times specified in models using comparison operators:

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

The script errors out with: 

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

The models look like this:

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

I also have django using locale date and times.

What I haven't been able to find is the format django uses for DateTimeField(). Is it naive or aware? And how do I get datetime.now() to recognize locale datetime?

codeforester
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sccrthlt
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    http://stackoverflow.com/questions/10652819/django-1-4-cant-compare-offset-naive-and-offset-aware-datetimes – catherine Mar 09 '13 at 05:50
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    possible duplicate of [Can't subtract offset-naive and offset-aware datetimes](http://stackoverflow.com/questions/796008/cant-subtract-offset-naive-and-offset-aware-datetimes) – PhoenixS Apr 09 '15 at 16:27
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    there is a very nice lib to play with date: pendulum (I am not affiliated) – Thomas Decaux Oct 08 '18 at 10:36

9 Answers9

238

By default, the datetime object is naive in Python, so you need to make both of them either naive or aware datetime objects. This can be done using:

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, and you can compare them

Note: This would raise a ValueError if tzinfo is already set. If you are not sure about that, just use

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

BTW, you could format a UNIX timestamp in datetime.datetime object with timezone info as following

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)
Phillip
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Viren Rajput
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    It says: ValueError: Not naive datetime (tzinfo is already set) when it tries to compute: datetimeStart = utc.localize(challenge.datetime_start) – sccrthlt Mar 09 '13 at 06:40
  • yep, it raises ValueError. – Dmitrii Mikhailov Jul 28 '15 at 17:47
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    Replacing the `tzinfo` doesn't do any conversion, making the comparison incorrect. – OrangeDog Nov 28 '17 at 13:25
  • +1 for this. And, using `utc = pytz.utc` to prevent the pylint error `No value for argument 'dt' in unbound method call (no-value-for-parameter)`. [pytz link](https://github.com/newvem/pytz/blob/master/pytz/__init__.py#L135) – sam Jul 05 '18 at 19:47
  • You can get `utc` timezone from `datetime`'s `timezone` module. `timezone.utc`. – mjuopperi Oct 20 '21 at 17:38
145

datetime.datetime.now is not timezone aware.

Django comes with a helper for this, which requires pytz

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

You should be able to compare now to challenge.datetime_start

Alfredo Aguirre
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    If `USE_TZ=True` then `timezone.now()` returns a timezone-aware datetime object even if `pytz` is not installed (though it might be recommended to install for other reasons). – jfs Jan 13 '16 at 10:31
  • This should be the accepted answer – AD Progress Apr 14 '22 at 22:28
100

One line of code solution

if timezone_aware_var <= datetime.datetime.now(timezone_aware_var.tzinfo):
    pass #some code

Explained version

# Timezone info of your timezone aware variable
timezone = your_timezone_aware_variable.tzinfo

# Current datetime for the timezone of your variable
now_in_timezone = datetime.datetime.now(timezone)

# Now you can do a fair comparison, both datetime variables have the same time zone
if your_timezone_aware_variable <= now_in_timezone:
    pass #some code

Summary

You must add the timezone info to your now() datetime.
However, you must add the same timezone of the reference variable; that is why I first read the tzinfo attribute.

ePi272314
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43

Disable time zone. Use challenge.datetime_start.replace(tzinfo=None);

You can also use replace(tzinfo=None) for other datetime.

if challenge.datetime_start.replace(tzinfo=None) <= datetime.now().replace(tzinfo=None) <= challenge.datetime_end.replace(tzinfo=None):
Hiren Gohel
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Amin Fathi
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5

no third-party, only the native datetime module.

from datetime import datetime, timedelta, timezone

time1 = datetime.strptime('2021-07-15T00:22:02+0000', '%Y-%m-%dT%H:%M:%S%z')
time2 = datetime(2021, 7, 15, tzinfo=timezone(offset=timedelta()))
if time1 < time2:
    print(True)
ovo
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3

It is working form me. Here I am geeting the table created datetime and adding 10 minutes on the datetime. later depending on the current time, Expiry Operations are done.

from datetime import datetime, time, timedelta
import pytz

Added 10 minutes on database datetime

table_datetime = '2019-06-13 07:49:02.832969' (example)

# Added 10 minutes on database datetime
# table_datetime = '2019-06-13 07:49:02.832969' (example)

table_expire_datetime = table_datetime + timedelta(minutes=10 )

# Current datetime
current_datetime = datetime.now()


# replace the timezone in both time
expired_on = table_expire_datetime.replace(tzinfo=utc)
checked_on = current_datetime.replace(tzinfo=utc)


if expired_on < checked_on:
    print("Time Crossed)
else:
    print("Time not crossed ")

It worked for me.

Chandan Sharma
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2

So the way I would solve this problem is to make sure the two datetimes are in the right timezone.

I can see that you are using datetime.now() which will return the systems current time, with no tzinfo set.

tzinfo is the information attached to a datetime to let it know what timezone it is in. If you are using naive datetime you need to be consistent through out your system. I would highly recommend only using datetime.utcnow()

seeing as somewhere your are creating datetime that have tzinfo associated with them, what you need to do is make sure those are localized (has tzinfo associated) to the correct timezone.

Take a look at Delorean, it makes dealing with this sort of thing much easier.

myusuf3
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1

You are trying to set the timezone for date_time which already has a timezone. Use replace and astimezone functions.

local_tz = pytz.timezone('Asia/Kolkata')

current_time = datetime.now().replace(tzinfo=pytz.utc).astimezone(local_tz)
Vitthal Sarode
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-1

Just:

dt = datetimeObject.strftime(format) # format = your datetime format ex) '%Y %d %m'
dt = datetime.datetime.strptime(dt,format)

So do this:

start_time = challenge.datetime_start.strftime('%Y %d %m %H %M %S')
start_time = datetime.datetime.strptime(start_time,'%Y %d %m %H %M %S')

end_time = challenge.datetime_end.strftime('%Y %d %m %H %M %S')
end_time = datetime.datetime.strptime(end_time,'%Y %d %m %H %M %S')

and then use start_time and end_time

Harispy
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