Can't subtract offset-naive and offset-aware datetimes

have you tried to remove the timezone awareness?

from http://pytz.sourceforge.net/

naive = dt.replace(tzinfo=None)

may have to add time zone conversion as well.

edit: Please be aware the age of this answer. An answer involving ADDing the timezone info instead of removing it in python 3 is below. https://stackoverflow.com/a/25662061/93380

The correct solution is to add the timezone info e.g., to get the current time as an aware datetime object in Python 3:

from datetime import datetime, timezone

now = datetime.now(timezone.utc)

On older Python versions, you could define the utc tzinfo object yourself (example from datetime docs):

from datetime import tzinfo, timedelta, datetime

ZERO = timedelta(0)

class UTC(tzinfo):
  def utcoffset(self, dt):
    return ZERO
  def tzname(self, dt):
    return "UTC"
  def dst(self, dt):
    return ZERO

utc = UTC()

then:

now = datetime.now(utc)

I know some people use Django specifically as an interface to abstract this type of database interaction. Django provides utilities that can be used for this:

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

You do need to set up a basic Django settings infrastructure, even if you are just using this type of interface (in settings, you need to include USE_TZ=True to get an aware datetime).

By itself, this is probably nowhere near enough to motivate you to use Django as an interface, but there are many other perks. On the other hand, if you stumbled here because you were mangling your Django app (as I did), then perhaps this helps...

This is a very simple and clear solution
Two lines of code

# First we obtain de timezone info o some datatime variable    

tz_info = your_timezone_aware_variable.tzinfo

# Now we can subtract two variables using the same time zone info
# For instance
# Lets obtain the Now() datetime but for the tz_info we got before

diff = datetime.datetime.now(tz_info)-your_timezone_aware_variable

Conclusion: You must mange your datetime variables with the same time info

You don't need anything outside the std libs

datetime.datetime.now().astimezone()

If you just replace the timezone it will not adjust the time. If your system is already UTC then .replace(tz='UTC') is fine.

>>> x=datetime.datetime.now()
datetime.datetime(2020, 11, 16, 7, 57, 5, 364576)

>>> print(x)
2020-11-16 07:57:05.364576

>>> print(x.astimezone()) 
2020-11-16 07:57:05.364576-07:00

>>> print(x.replace(tzinfo=datetime.timezone.utc)) # wrong
2020-11-16 07:57:05.364576+00:00