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

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

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.