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.

Answer 2

我只是猜测，但一小时的差异可能不是因为时区，而是因为开启/关闭夏令时。

Answer 3

naive_utc_dt = parseddate.replace(tzinfo=None)
timestamp = (naive_utc_dt - datetime(1970, 1, 1)).total_seconds()
# -> 1247793660.0

See more details in another answer to similar question .

And back:

utc_dt = datetime.utcfromtimestamp(timestamp)
# -> datetime.datetime(2009, 7, 17, 1, 21)

Answer 4

import time
import datetime
import calendar

def date_time_to_utc_epoch(dt_utc):         #convert from utc date time object (yyyy-mm-dd hh:mm:ss) to UTC epoch
    frmt="%Y-%m-%d %H:%M:%S"
    dtst=dt_utc.strftime(frmt)              #convert datetime object to string
    time_struct = time.strptime(dtst, frmt) #convert time (yyyy-mm-dd hh:mm:ss) to time tuple
    epoch_utc=calendar.timegm(time_struct)  #convert time to to epoch
    return epoch_utc

#----test function --------
now_datetime_utc = int(date_time_to_utc_epoch(datetime.datetime.utcnow()))
now_time_utc = int(time.time())

print (now_datetime_utc)
print (now_time_utc)

if now_datetime_utc == now_time_utc : 
    print ("Passed")  
else : 
    print("Failed")