How can I get the current time (now) in UTC?

Use the following:

from datetime import timezone
utc_datetime = local_datetime.astimezone().astimezone(timezone.utc).replace(tzinfo=None)

Given a naive datetime object assumed to have a local datetime, you can use the following sequence of method calls to convert it to a naive UTC datetime representing the same UTC time (tested with Python 3.6.3).

1. astimezone() to add the local timezone so it's no longer naive.
2. astimezone(timezone.utc) to convert it from local to UTC.
3. replace(tzinfo=None) to remove the timezone so it's naive again, but now UTC

Example:

>>> local_datetime = datetime.now()
>>> local_datetime
datetime.datetime(2019, 12, 14, 10, 30, 37, 91818)
>>> local_datetime.astimezone()
datetime.datetime(2019, 12, 14, 10, 30, 37, 91818, tzinfo=datetime.timezone(datetime.timedelta(-1, 68400), 'Eastern Standard Time'))
>>> local_datetime.astimezone().astimezone(timezone.utc)
datetime.datetime(2019, 12, 14, 15, 30, 37, 91818, tzinfo=datetime.timezone.utc)
>>> local_datetime.astimezone().astimezone(timezone.utc).replace(tzinfo=None)
datetime.datetime(2019, 12, 14, 15, 30, 37, 91818)

Note: The first astimezone() is not really needed because of this note in the Python docs:

Changed in version 3.6: The astimezone() method can now be called on naive instances that are presumed to represent system local time.

For those who ended up here looking for a way to convert a datetime object to UTC seconds since UNIX epoch:

import time
import datetime

t = datetime.datetime.now()
utc_seconds = time.mktime(t.timetuple())

First you need to make sure the datetime is a timezone-aware object by setting its tzinfo member:

http://docs.python.org/library/datetime.html#datetime.tzinfo

You can then use the .astimezone() function to convert it:

http://docs.python.org/library/datetime.html#datetime.datetime.astimezone

Run this to obtain a naive datetime in UTC (and to add five minutes to it):

>>> from datetime import datetime, timedelta
>>> datetime.utcnow()
datetime.datetime(2021, 1, 26, 15, 41, 52, 441598)
>>> datetime.utcnow() + timedelta(minutes=5)
datetime.datetime(2021, 1, 26, 15, 46, 52, 441598)

If you would prefer a timezone-aware datetime object, run this in Python 3.2 or higher:

>>> from datetime import datetime, timezone
>>> datetime.now(timezone.utc)
datetime.datetime(2021, 1, 26, 15, 43, 54, 379421, tzinfo=datetime.timezone.utc)