Date/time conversion using time.mktime seems wrong

Question

>>> import time
>>> time.strptime("01-31-2009", "%m-%d-%Y")
(2009, 1, 31, 0, 0, 0, 5, 31, -1)
>>> time.mktime((2009, 1, 31, 0, 0, 0, 5, 31, -1))
1233378000.0
>>> 60*60*24 # seconds in a day
86400
>>> 1233378000.0 / 86400
14275.208333333334

time.mktime should return the number of seconds since the epoch. Since I'm giving it a time at midnight and the epoch is at midnight, shouldn't the result be evenly divisible by the number of seconds in a day?

Answer 1

Short answer: Because of timezones.

The Epoch is in UTC.

For example, I'm on IST (Irish Standard Time) or UTC+1. time.mktime() is relative to my timezone, so on my system this refers to

>>> time.mktime((2009, 1, 31, 0, 0, 0, 5, 31, -1))
1233360000.0

Because you got the result 1233378000, that would suggest that you're 5 hours behind me

>>> (1233378000 - 1233360000) / (60*60)    
5

Have a look at the time.gmtime() function which works off UTC.