How to specify time zone (UTC) when converting to Unix time? (Python)

Question

I have a utc timestamp in the IS8601 format and am trying to convert it to unix time. This is my console session:

In [9]: mydate
Out[9]: '2009-07-17T01:21:00.000Z'
In [10]: parseddate = iso8601.parse_date(mydate)

In [14]: ti = time.mktime(parseddate.timetuple())

In [25]: datetime.datetime.utcfromtimestamp(ti)
Out[25]: datetime.datetime(2009, 7, 17, 7, 21)
In [26]: datetime.datetime.fromtimestamp(ti)
Out[26]: datetime.datetime(2009, 7, 17, 2, 21)

In [27]: ti
Out[27]: 1247815260.0
In [28]: parseddate
Out[28]: datetime.datetime(2009, 7, 17, 1, 21, tzinfo=<iso8601.iso8601.Utc object at 0x01D74C70>)

As you can see, I can't get the correct time back. The hour is ahead by one if i use fromtimestamp(), and it's ahead by six hours if i use utcfromtimestamp()

Any advice?

Thanks!

Answer 1

You can create an struct_time in UTC with datetime.utctimetuple() and then convert this to a unix timestamp with calendar.timegm():

calendar.timegm(parseddate.utctimetuple())

This also takes care of any daylight savings time offset, because utctimetuple() normalizes this.