337

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?

Benjamin Loison
  • 3,782
  • 4
  • 16
  • 33
sccrthlt
  • 3,974
  • 5
  • 20
  • 24
  • 2
    http://stackoverflow.com/questions/10652819/django-1-4-cant-compare-offset-naive-and-offset-aware-datetimes – catherine Mar 09 '13 at 05:50
  • 3
    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
  • 1
    there is a very nice lib to play with date: pendulum (I am not affiliated) – Thomas Decaux Oct 08 '18 at 10:36

14 Answers14

302

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)
ballade4op52
  • 2,142
  • 5
  • 27
  • 42
Viren Rajput
  • 5,426
  • 5
  • 30
  • 41
  • 2
    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
  • 11
    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
  • 2
    You can get `utc` timezone from `datetime`'s `timezone` module. `timezone.utc`. – mjuopperi Oct 20 '21 at 17:38
  • 1
    Only use the "replace()" method if you already know that both values are in UTC, but *don't* know if they are both offset-aware datetimes. I'm working in a system where a .NET application is passing data to a Python API, and sometimes the .NET datetimes have an offset like "+00:00" and sometimes they don't, but they are still in UTC. Using `datetime.parse()` on a date with the offset creates an offset-aware datetime object in Python, which throws an error if I try to compare it to a `datetime.parse()` on a string without the "+00:00". – jwatts1980 Jan 19 '23 at 05:24
  • What does _naive_ and _aware_ mean in this context? – Nils Lindemann Sep 01 '23 at 10:55
169

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
  • 1,906
  • 1
  • 10
  • 7
  • 8
    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
130

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
  • 12,557
  • 5
  • 50
  • 36
54

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
  • 4,942
  • 6
  • 29
  • 48
Amin Fathi
  • 551
  • 4
  • 6
13

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
  • 1,904
  • 13
  • 26
4

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
  • 2,321
  • 22
  • 22
2

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
  • 89
  • 4
2

To make your datetime object timezone aware from naive, simply add the function:

datetimeObject.astimezone()
Saurabh Deshmukh
  • 68
  • 7
1

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.

Mahdi Yusuf
  • 19,931
  • 26
  • 72
  • 101
1

If you are using SQLAlchemy and storing the DateTime then you can store it with timezone info. This will allow you to compare that DateTime with timezone-aware DateTimes. Example Column definition in SQLAlchemy core:

Column("created_at", DateTime(timezone=True), nullable=False)
Bartłomiej Skwira
  • 1,701
  • 1
  • 16
  • 24
1

If you're using Python 3.6 and newer, you can leverage the native datetime capability.

utc_date = datetime.datetime.fromtimestamp(0, datetime.timezone.utc)
Jan Richter
  • 1,976
  • 4
  • 29
  • 49
  • Could you provide an example for an actual date to see what the input should look like? Seems clearer to provide the `tzinfo` in the `datetime` method. – Seb Dec 12 '22 at 15:14
  • 1
    Sure, you can find the examples in the documentation here: https://docs.python.org/3/library/datetime.html#datetime.datetime.fromisoformat – Jan Richter Dec 16 '22 at 01:01
0

In my case I have controlled the time zone with pytz and I have converted the date to native with timezone from django.utils:

import pytz
from django.utils import timezone

def _my_method(native_date, timezone):
    aware_date = datetime.now(pytz.timezone(timezone))
    return timezone.make_naive(aware_date) >  native_date

Also you can make aware the native date with timezone.make_aware

IvanAllue
  • 434
  • 3
  • 11
0

From time to time this error pops up in my notebooks... I have no clue why.

My datetime objects are usually in arrays. I tried some of the answers above, but the way I found to deal with this problem is

import numpy as np
import matplotlib.dates as mdates

array_with_datetime = np.array( 
                          mdates.num2date( 
                                     mdates.date2num( 
                                                 array_with_datetime)))

not elegant, but it works. If I not use the np.array, it returns a list.

Carlos Augusto Frana Schettini
  • 153
  • 1
  • 9
-2

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
  • 1
  • 1