pythondatetimeutclocaltime

How to convert local time string to UTC?

How do I convert a datetime string in local time to a string in UTC time?

I'm sure I've done this before, but can't find it and SO will hopefully help me (and others) do that in future.

Clarification: For example, if I have 2008-09-17 14:02:00 in my local timezone (+10), I'd like to generate a string with the equivalent UTC time: 2008-09-17 04:02:00.

Also, from http://lucumr.pocoo.org/2011/7/15/eppur-si-muove/, note that in general this isn't possible as with DST and other issues there is no unique conversion from local time to UTC time.

Solution

  • Thanks @rofly, the full conversion from string to string is as follows:

    import time
time.strftime("%Y-%m-%d %H:%M:%S", 
              time.gmtime(time.mktime(time.strptime("2008-09-17 14:04:00", 
                                                    "%Y-%m-%d %H:%M:%S"))))

    My summary of the time/calendar functions:

    time.strptime
    string --> tuple (no timezone applied, so matches string)

    time.mktime
    local time tuple --> seconds since epoch (always local time)

    time.gmtime
    seconds since epoch --> tuple in UTC

    and

    calendar.timegm
    tuple in UTC --> seconds since epoch

    time.localtime
    seconds since epoch --> tuple in local timezone