Incorrect results of converting between python datetime and timestamp

Question

The output of following code is totally wrong:

import time
from datetime import datetime

def sec_to_date(sec, format="%m/%d/%Y %H:%M:%S"):
    tmp = datetime.fromtimestamp(sec)
    fmtdate = tmp.strftime(format)
    return fmtdate

def date_to_sec(fmtdate, format="%m/%d/%Y %H:%M:%S"):
    t_tuple = time.strptime(fmtdate, format)
    sec = time.mktime(t_tuple)
    return sec

if __name__ == "__main__":
    fmtdate = sec_to_date(1380204000)
    print "1380204000 sec to date " + fmtdate
    fmtdate = sec_to_date(1388355120)
    print "1388355120 sec to date " + fmtdate
    sec = date_to_sec("09/26/2013 10:00:00")
    print "09/26/2013 10:00:00 to " + str(sec) + " sec"
    sec = date_to_sec("12/29/2013 17:12:00")
    print "12/29/2013 17:12:00 to " + str(sec) + " sec"

Here is the output:

1380204000 sec to date 09/26/2013 10:00:00
1388355120 sec to date 12/29/2013 17:12:00
09/26/2013 10:00:00 to 1380204000.0 sec
12/29/2013 17:12:00 to 1388355120.0 sec

The difference between two timestamps, 1380204000 and 1388355120, should be 94 days and 8.2 hours, while my results show a difference of 94 days and 7.2 hours. Any idea what happened?

I think you're mistaken. The time difference between 10:00:00 and 17:12:00 is 7.2 hours. — Cyphase
– Cyphase, Commented Aug 20, 2015 at 1:49
@Cyphase Yes, it is 7.2 hours, but the difference between 1380204000 and 1388355120 should be 94days + 8.2hours, not 7.2hours — roymaztang
– roymaztang, Commented Aug 20, 2015 at 1:51

Cyphase · Accepted Answer · 2015-08-20 01:56:59Z

2

Your issue is Daylight Saving Time. The time between the timestamps is indeed 94 days, 8.2 hours; but given DST, that means the formatted hour of the later time will be an hour behind where you expect.

answered Aug 20, 2015 at 1:56

Cyphase

12k3 gold badges33 silver badges33 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Incorrect results of converting between python datetime and timestamp

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related