How do I use timezones with a datetime object in python?

jidar_9338 0
Viewed 47781

How do I properly represent a different timezone in my timezone? The below example only works because I know that EDT is one hour ahead of me, so I can uncomment the subtraction of myTimeZone()

import datetime, re
from datetime import tzinfo

class myTimeZone(tzinfo):
    """docstring for myTimeZone"""
    def utfoffset(self, dt):
        return timedelta(hours=1)

def myDateHandler(aDateString):
    """u'Sat,  6 Sep 2008 21:16:33 EDT'"""
    _my_date_pattern = re.compile(r'\w+\,\s+(\d+)\s+(\w+)\s+(\d+)\s+(\d+)\:(\d+)\:(\d+)')
    day, month, year, hour, minute, second = _my_date_pattern.search(aDateString).groups()
    month = [
            'JAN', 'FEB', 'MAR', 
            'APR', 'MAY', 'JUN', 
            'JUL', 'AUG', 'SEP', 
            'OCT', 'NOV', 'DEC'
    ].index(month.upper()) + 1
    dt = datetime.datetime(
        int(year), int(month), int(day), 
        int(hour), int(minute), int(second)
    )                   
    # dt = dt - datetime.timedelta(hours=1)
    # dt = dt - dt.tzinfo.utfoffset(myTimeZone())
    return (dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second, 0, 0, 0)

def main():
    print myDateHandler("Sat,  6 Sep 2008 21:16:33 EDT")

if __name__ == '__main__':
    main()
timezone datetime python
4 Answers

I recommend babel and pytz when working with timezones. Keep your internal datetime objects naive and in UTC and convert to your timezone for formatting only. The reason why you probably want naive objects (objects without timezone information) is that many libraries and database adapters have no idea about timezones.

Armin_Ronacher_199900

The Python standard library doesn't contain timezone information, because unfortunately timezone data changes a lot faster than Python. You need a third-party module for this; the usual choice is pytz

Thomas_Wouters_176240

For the current local timezone, you can you use:

>>> import time
>>> offset = time.timezone if (time.localtime().tm_isdst == 0) else time.altzone
>>> offset / 60 / 60 * -1
-9

The value returned is in seconds West of UTC (with areas East of UTC getting a negative value). This is the opposite to how we'd actually like it, hence the * -1.

localtime().tm_isdst will be zero if daylight savings is currently not in effect (although this may not be correct if an area has recently changed their daylight savings law).

user_2687890

Python >= 3.9

Python comes with zoneinfo as part of the standard lib. Example usage:

from datetime import datetime, timezone
from zoneinfo import ZoneInfo
UTC = datetime(2012,11,10,9,0,0, tzinfo=timezone.utc)

# convert to another tz with "astimezone":
eastern = UTC.astimezone(ZoneInfo("US/Eastern"))

# note that it is safe to use "replace",
# to get the same wall time in a different tz:
pacific = eastern.replace(tzinfo=ZoneInfo("US/Pacific"))

print(UTC.isoformat())
print(eastern.isoformat())
print(pacific.isoformat())

# 2012-11-10T09:00:00+00:00
# 2012-11-10T04:00:00-05:00
# 2012-11-10T04:00:00-08:00

Also note this section from the docs:

The zoneinfo module does not directly provide time zone data, and instead pulls time zone information from the system time zone database or the first-party PyPI package tzdata, if available.

So don't forget to call a pip install tzdata, on Windows at least.

user_101974180
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