I am trying to subtract one date value from the value of
datetime.datetime.today() to calculate how long ago something was. But it complains:
TypeError: can't subtract offset-naive and offset-aware datetimes
The return value from
datetime.datetime.today() doesn’t seem to be "timezone aware", while my other date value is. How do I get a return value from
datetime.datetime.today() that is timezone aware?
The ideal solution would be for it to automatically know the timezone.
Right now, it’s giving me the time in local time, which happens to be PST, i.e. UTC – 8 hours. Worst case, is there a way I can manually enter a timezone value into the
datetime object returned by
datetime.datetime.today() and set it to UTC-8?
In the standard library, there is no cross-platform way to create aware timezones without creating your own timezone class. (Edit: Python 3.9 introduces
zoneinfo in the standard library which does provide this functionality.)
On Windows, there’s
win32timezone.utcnow(), but that’s part of pywin32. I would rather suggest to use the pytz library, which has a constantly updated database of most timezones.
Working with local timezones can be very tricky (see "Further reading" links below), so you may rather want to use UTC throughout your application, especially for arithmetic operations like calculating the difference between two time points.
You can get the current date/time like so:
import pytz from datetime import datetime datetime.utcnow().replace(tzinfo=pytz.utc)
datetime.now() return the local time, not the UTC time, so applying
.replace(tzinfo=pytz.utc) to them would not be correct.
Another nice way to do it is:
which is a bit shorter and does the same.
Further reading/watching why to prefer UTC in many cases:
Another method to construct time zone aware datetime object representing current time:
import datetime import pytz pytz.utc.localize( datetime.datetime.utcnow() )
You can install
pytz from PyPI by running:
$ pipenv install pytz
Get the current time, in a specific timezone:
import datetime import pytz my_date = datetime.datetime.now(pytz.timezone('US/Pacific'))
Remember to install
If you are using Django, you can set dates non-tz aware (only UTC).
Comment the following line in settings.py:
USE_TZ = True
Here’s a stdlib solution that works on both Python 2 and 3:
from datetime import datetime now = datetime.now(utc) # Timezone-aware datetime.utcnow() today = datetime(now.year, now.month, now.day, tzinfo=utc) # Midnight
today is an aware datetime instance representing the beginning of the day (midnight) in UTC and
utc is a tzinfo object (example from the documentation):
from datetime import tzinfo, timedelta 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()
Related: performance comparison of several ways to get midnight (start of a day) for a given UTC time.
Note: it is more complex, to get midnight for a time zone with a non-fixed UTC offset.
Use dateutil as described in Python datetime.datetime.now() that is timezone aware:
from dateutil.tz import tzlocal # Get the current date/time with the timezone. now = datetime.datetime.now(tzlocal())
Getting a timezone-aware date in
utc timezone is enough for date subtraction to work.
But if you want a timezone-aware date in your current time zone,
tzlocal is the way to go:
from tzlocal import get_localzone # pip install tzlocal from datetime import datetime datetime.now(get_localzone())
dateutil has a similar function (
dateutil.tz.tzlocal). But inspite of sharing the name it has a completely different code base, which as noted by J.F. Sebastian can give wrong results.
Here is one way to generate it with the stdlib:
import time from datetime import datetime FORMAT='%Y-%m-%dT%H:%M:%S%z' date=datetime.strptime(time.strftime(FORMAT, time.localtime()),FORMAT)
date will store the local date and the offset from UTC, not the date at UTC timezone, so you can use this solution if you need to identify which timezone the date is generated at. In this example and in my local timezone:
date datetime.datetime(2017, 8, 1, 12, 15, 44, tzinfo=datetime.timezone(datetime.timedelta(0, 7200))) date.tzname() 'UTC+02:00'
The key is adding the
%z directive to the representation FORMAT, to indicate the UTC offset of the generated time struct. Other representation formats can be consulted in the datetime module docs
If you need the date at the UTC timezone, you can replace time.localtime() with time.gmtime()
date=datetime.strptime(time.strftime(FORMAT, time.gmtime()),FORMAT) date datetime.datetime(2017, 8, 1, 10, 23, 51, tzinfo=datetime.timezone.utc) date.tzname() 'UTC'
This works only on python3. The z directive is not available on python 2 _strptime.py code
The standard library makes it much easier to specify UTC as the time zone:
>>> import datetime >>> datetime.datetime.now(datetime.timezone.utc) datetime.datetime(2020, 11, 27, 14, 34, 34, 74823, tzinfo=datetime.timezone.utc)
You can also get a datetime that includes the local time offset using
>>> datetime.datetime.now(datetime.timezone.utc).astimezone() datetime.datetime(2020, 11, 27, 15, 34, 34, 74823, tzinfo=datetime.timezone(datetime.timedelta(seconds=3600), 'CET'))
(In Python 3.6+, you can shorten the last line to:
If you want a solution that uses only the standard library and that works in both Python 2 and Python 3, see jfs’ answer.
zoneinfoto use the IANA time zone database:
In Python 3.9, you can specify particular time zones using the standard library, using
zoneinfo, like this:
>>> from zoneinfo import ZoneInfo >>> datetime.datetime.now(ZoneInfo("America/Los_Angeles")) datetime.datetime(2020, 11, 27, 6, 34, 34, 74823, tzinfo=zoneinfo.ZoneInfo(key='America/Los_Angeles'))
zoneinfo gets its database of time zones from the operating system, or from the first-party PyPI package
tzdata if available.
If you get current time and date in python then import date and time,pytz package in python after you will get current date and time like as..
from datetime import datetime import pytz import time str(datetime.strftime(datetime.now(pytz.utc),"%Y-%m-%d %H:%M:%S%t"))
from datetime import datetime, timezone aware_local_now = datetime.now(timezone.utc).astimezone() print(aware_local_now) # 2020-03-03 09:51:38.570162+01:00 print(repr(aware_local_now)) # datetime.datetime(2020, 3, 3, 9, 51, 38, 570162, tzinfo=datetime.timezone(datetime.timedelta(0, 3600), 'CET'))
Another alternative, in my mind a better one, is using
Pendulum instead of
pytz. Consider the following simple code:
>>> import pendulum >>> dt = pendulum.now().to_iso8601_string() >>> print (dt) 2018-03-27T13:59:49+03:00 >>>
To install Pendulum and see their documentation, go here. It have tons of options (like simple ISO8601, RFC3339 and many others format support), better performance and tend to yield simpler code.
Use the timezone as shown below for a timezone-aware date time. The default is UTC:
from django.utils import timezone today = timezone.now()
Especially for non-UTC timezones:
The only timezone that has its own method is
timezone.utc, but you can fudge a timezone with any UTC offset if you need to by using
timezone, and forcing it using
In : from datetime import datetime, timezone, timedelta In : def force_timezone(dt, utc_offset=0): ...: return dt.replace(tzinfo=timezone(timedelta(hours=utc_offset))) ...: In : dt = datetime(2011,8,15,8,15,12,0) In : str(dt) Out: '2011-08-15 08:15:12' In : str(force_timezone(dt, -8)) Out: '2011-08-15 08:15:12-08:00'
timezone(timedelta(hours=n)) as the time zone is the real silver bullet here, and it has lots of other useful applications.
Here is a solution using a readable timezone and that works with today():
from pytz import timezone datetime.now(timezone('Europe/Berlin')) datetime.now(timezone('Europe/Berlin')).today()
You can list all timezones as follows:
import pytz pytz.all_timezones pytz.common_timezones # or
Tyler from ‘howchoo’ made a really great article that helped me get a better idea of the Datetime Objects, link below
essentially, I just added the following to the end of both my datetime objects
import pytz import datetime from datetime date = datetime.now().replace(tzinfo=pytz.utc)
try pnp_datetime, all the time been used and returned is with timezone, and will not cause any offset-naive and offset-aware issues.
>>> from pnp_datetime.pnp_datetime import Pnp_Datetime >>> >>> Pnp_Datetime.utcnow() datetime.datetime(2020, 6, 5, 12, 26, 18, 958779, tzinfo=<UTC>)
It should be emphasized that since Python 3.6, you only need the standard lib to get a timezone aware datetime object that represents local time (the setting of your OS). Using astimezone()
import datetime datetime.datetime(2010, 12, 25, 10, 59).astimezone() # e.g. # datetime.datetime(2010, 12, 25, 10, 59, tzinfo=datetime.timezone(datetime.timedelta(seconds=3600), 'Mitteleuropäische Zeit')) datetime.datetime(2010, 12, 25, 12, 59).astimezone().isoformat() # e.g. # '2010-12-25T12:59:00+01:00' # I'm on CET/CEST
(see @johnchen902’s comment). Note there’s a small caveat though, astimezone(None) gives aware datetime, unaware of DST.