Converting timezone-aware datetime to local time in Python
Solution 1
In general, to convert an arbitrary timezone-aware datetime to a naive (local) datetime, I'd use the pytz
module and astimezone
to convert to local time, and replace
to make the datetime naive:
In [76]: import pytz
In [77]: est=pytz.timezone('US/Eastern')
In [78]: d.astimezone(est)
Out[78]: datetime.datetime(2010, 10, 30, 13, 21, 12, tzinfo=<DstTzInfo 'US/Eastern' EDT-1 day, 20:00:00 DST>)
In [79]: d.astimezone(est).replace(tzinfo=None)
Out[79]: datetime.datetime(2010, 10, 30, 13, 21, 12)
But since your particular datetime seems to be in the UTC timezone, you could do this instead:
In [65]: d
Out[65]: datetime.datetime(2010, 10, 30, 17, 21, 12, tzinfo=tzutc())
In [66]: import datetime
In [67]: import calendar
In [68]: datetime.datetime.fromtimestamp(calendar.timegm(d.timetuple()))
Out[68]: datetime.datetime(2010, 10, 30, 13, 21, 12)
By the way, you might be better off storing the datetimes as naive UTC datetimes instead of naive local datetimes. That way, your data is local-time agnostic, and you only convert to local-time or any other timezone when necessary. Sort of analogous to working in unicode as much as possible, and encoding only when necessary.
So if you agree that storing the datetimes in naive UTC is the best way, then all you'd need to do is define:
local_d = d.replace(tzinfo=None)
Solution 2
In recent versions of Django (at least 1.4.1):
from django.utils.timezone import localtime
result = localtime(some_time_object)
Solution 3
A portable robust solution should use the tz database. To get local timezone as pytz
tzinfo
object, use tzlocal
module:
#!/usr/bin/env python
import iso8601
import tzlocal # $ pip install tzlocal
local_timezone = tzlocal.get_localzone()
aware_dt = iso8601.parse_date("2010-10-30T17:21:12Z") # some aware datetime object
naive_local_dt = aware_dt.astimezone(local_timezone).replace(tzinfo=None)
Note: it might be tempting to use something like:
#!/usr/bin/env python3
# ...
naive_local_dt = aware_dt.astimezone().replace(tzinfo=None)
but it may fail if the local timezone has a variable utc offset but python does not use a historical timezone database on a given platform.
Solution 4
Using python-dateutil
you can parse the date in iso-8561 format with dateutil.parsrser.parse()
that will give you an aware datetime
in UTC/Zulu timezone.
Using .astimezone()
you can convert it to an aware datetime in another timezone.
Using .replace(tzinfo=None)
will convert the aware datetime into a naive datetime.
from datetime import datetime
from dateutil import parser as datetime_parser
from dateutil.tz import tzutc,gettz
aware = datetime_parser.parse('2015-05-20T19:51:35.998931Z').astimezone(gettz("CET"))
naive = aware.replace(tzinfo=None)
In general the best idea is to convert all dates to UTC and store them that way, and convert them back to local as needed. I use aware.astimezone(tzutc()).replace(tzinfo=None)
to make sure is in UTC and convert to naive.
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kes
Updated on September 30, 2020Comments
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kes over 3 years
How do you convert a timezone-aware datetime object to the equivalent non-timezone-aware datetime for the local timezone?
My particular application uses Django (although, this is in reality a generic Python question):
import iso8601
....
date_str="2010-10-30T17:21:12Z"
....
d = iso8601.parse_date(date_str) foo = app.models.FooModel(the_date=d) foo.save()
This causes Django to throw an error:
raise ValueError("MySQL backend does not support timezone-aware datetimes.")
What I need is:
d = iso8601.parse_date(date_str) local_d = SOME_FUNCTION(d) foo = app.models.FooModel(the_date=local_d)
What would SOME_FUNCTION be?
-
jfs over 9 years
-
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kes about 13 yearsYes, I did ultimately decide to store the dates as naive UTC. You've answered both questions I had about that (stripping tzinfo and converting timezone), so thanks!
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jfs over 9 years
localtime()
may usesettings.TIME_ZONE
that may be different from the local timezone e.g., if you haven't set it then it is'America/Chicago'
by default. Iflocaltime()
does not usesettings.TIME_ZONE
then it uses broken (according to its documentation)LocalTimezone()
-
jfs over 9 years
fromtimestamp()
may fail for dates from the past (if UTC offset was different at the time in the local timezone) if it doesn't use the tz database to find UTC offset (It does on Ubuntu, I'm not sure about Windows). -
jfs over 8 years
-
RubenLaguna over 8 yearsSee that the whole issue of PEP-0495 Local Time Dissambiguation is a bit hairy in general. After reading issue #57 I understand that
tzlocal
is smarter and tries to figure out your real system timezone settings to dissambiguate, which probably is what most of the people would like. -
jfs over 8 yearsIt is not about how smart they are: both
tzlocal.get_localzone()
anddateutil.tz.tzlocal()
may load their data from the same tzdata file. The bugs are due to an inherit limitation indateutil
approach to how timezone-aware datetime objects are interpreted (this approach requires PEP 495 to disambiguate even unambiguous conversions such as utc -> local).pytz
works today (get_localzone()
returnspytz
tzinfo objects). -
Cerin over 5 years
ValueError: astimezone() cannot be applied to a naive datetime