I'm trying to convert "Europe/London" pytz timezone to UTC without success:
>>>tz=pytz.timezone("Europe/London")
>>>date=datetime.datetime(2015,1,1,4,4)
>>>tz.normalize(tz.localize(date)).astimezone(pytz.utc)
datetime.datetime(2015, 1, 1, 4, 4, tzinfo=<UTC>)
>>>tz.localize(date)
datetime.datetime(2015, 1, 1, 4, 4, tzinfo=<DstTzInfo 'Europe/London'GMT0:00:00 STD>)
This is just flat out wrong, why is the line directly above at GMT-0 when it should be GMT+1. London time is currently one hour ahead of UTC because of daylights savings but the code isn't producing this.
>>>tz.normalize(tz.localize(date)).astimezone(pytz.utc) #should produce:
datetime.datetime(2015, 1, 1, 3, 4, tzinfo=<UTC>)
You shouldn't expect the summer time in January in the Northern Hemisphere in London.
pytz-2015.4 version produces the same (correct) result:
>>> from datetime import datetime
>>> import pytz
>>> d = datetime(2015, 1, 1, 4, 4)
>>> tz = pytz.timezone('Europe/London')
>>> tz.localize(d, is_dst=None).astimezone(pytz.utc)
datetime.datetime(2015, 1, 1, 4, 4, tzinfo=<UTC>)
>>> tz.localize(d, is_dst=None)
datetime.datetime(2015, 1, 1, 4, 4, tzinfo=<DstTzInfo 'Europe/London' GMT0:00:00 STD>)
zdump on my system agrees with it:
$ zdump -v Europe/London | grep 2015
Europe/London Sun Mar 29 00:59:59 2015 UT = Sun Mar 29 00:59:59 2015 GMT isdst=0 gmtoff=0
Europe/London Sun Mar 29 01:00:00 2015 UT = Sun Mar 29 02:00:00 2015 BST isdst=1 gmtoff=3600
Europe/London Sun Oct 25 00:59:59 2015 UT = Sun Oct 25 01:59:59 2015 BST isdst=1 gmtoff=3600
Europe/London Sun Oct 25 01:00:00 2015 UT = Sun Oct 25 01:00:00 2015 GMT isdst=0 gmtoff=0
i.e., until March 29, 2015 the utc offset is zero in London.
The tz database itself agrees: Europe/London uses EU rules for DST transitions since 1996: the summer time doesn't start until the last Sunday in March.