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pythonutcpython-2.6gmtpytz
curlyreggie
curlyreggie

Reputation: 1530

Convert GMT based time to UTC python

I get a date like 2014/08/19 03:38:46 GMT-4 from the database.

How do I convert this into UTC formatted date in Python?

PS: I use Python 2.6.6

Upvotes: 1

Views: 10043

Answers (2)

jfs
jfs

Reputation: 414885

GMT-4 is ambiguous: is it time in America/New_Your (-0400 utc offset) or in Europe/Moscow (+0400)?

$ TZ=GMT-4 date +%Z%z
GMT+0400
$ TZ=UTC-4 date +%Z%z
UTC+0400
$ TZ=America/New_York date +%Z%z
EDT-0400
$ TZ=Europe/Moscow date +%Z%z
MSK+0400

Your comment suggests that you need the sign of the utc offset reversed.

Python 2.6 has no fixed-offset timezones in stdlib. You could use the example implementation from the datetime docs:

from datetime import tzinfo, timedelta, datetime

ZERO = timedelta(0)

class FixedOffset(tzinfo):
    """Fixed UTC offset: `local = utc + offset`."""

    def __init__(self, offset, name):
        self.__offset = timedelta(hours=offset)
        self.__name = name

    def utcoffset(self, dt):
        return self.__offset

    def tzname(self, dt):
        return self.__name

    def dst(self, dt):
        return ZERO

utc = FixedOffset(0, "UTC")

Then to parse the time string, you could use strptime():

dt = datetime.strptime("2014/08/19 03:38:46 GMT-4", "%Y/%m/%d %H:%M:%S GMT-4")
aware = dt.replace(tzinfo=FixedOffset(-4, "GMT-4"))
print(aware)                 # -> 2014-08-19 03:38:46-04:00
print(aware.astimezone(utc)) # -> 2014-08-19 07:38:46+00:00

Upvotes: 1

xecgr
xecgr

Reputation: 5193

Having a non-naive datetime object, you only should invoke astimezone method with desired timezone

>>> import pytz
>>> from dateutil import parser
# dateutil.parser get a datetime object from string, we ensure that is a non-naive datetime
>>> parser.parse('2014/08/19 03:38:46 GMT-4')
datetime.datetime(2014, 8, 19, 3, 38, 46, tzinfo=tzoffset(None, 14400))
>>> dt = parser.parse('2014/08/19 03:38:46 GMT-4')
>>> dt.astimezone (pytz.utc)
datetime.datetime(2014, 8, 18, 23, 38, 46, tzinfo=<UTC>)

You are right in your comment, utc time should go behind, so while I think another solution, what about this

>>> dt = parser.parse('2014/08/19 03:38:46 GMT-4')
>>> dt.replace(tzinfo=pytz.utc) + dt.tzinfo._offset
datetime.datetime(2014, 8, 19, 7, 38, 46, tzinfo=<UTC>)

Upvotes: 4

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