Why does datetime.datetime.utcnow() not contain timezone information?

Question

datetime.datetime.utcnow() 

Why does this datetime not have any timezone info given that it is explicitly a UTC datetime?

I would expect that this would contain tzinfo.

Answer 1

Note that for Python 3.2 onwards, the datetime module contains datetime.timezone. The documentation for datetime.utcnow() says:

An aware current UTC datetime can be obtained by calling datetime.now(timezone.utc).

So, datetime.utcnow() doesn't set tzinfo to indicate that it is UTC, but datetime.now(datetime.timezone.utc) does return UTC time with tzinfo set.

So you can do:

>>> import datetime >>> datetime.datetime.now(datetime.timezone.utc) datetime.datetime(2014, 7, 10, 2, 43, 55, 230107, tzinfo=datetime.timezone.utc) 

Answer 2

That means it is timezone naive, so you can't use it with datetime.astimezone

you can give it a timezone like this

import pytz  # 3rd party: $ pip install pytz  u = datetime.utcnow() u = u.replace(tzinfo=pytz.utc) #NOTE: it works only with a fixed utc offset 

now you can change timezones

print(u.astimezone(pytz.timezone("America/New_York"))) 

To get the current time in a given timezone, you could pass tzinfo to datetime.now() directly:

#!/usr/bin/env python from datetime import datetime import pytz # $ pip install pytz  print(datetime.now(pytz.timezone("America/New_York"))) 

It works for any timezone including those that observe daylight saving time (DST) i.e., it works for timezones that may have different utc offsets at different times (non-fixed utc offset). Don't use tz.localize(datetime.now()) -- it may fail during end-of-DST transition when the local time is ambiguous.