Convert python datetime to epoch with strftime

251
votes

I have a time in UTC from which I want the number of seconds since epoch.

I am using strftime to convert it to the number of seconds. Taking 1st April 2012 as an example.

>>>datetime.datetime(2012,04,01,0,0).strftime('%s')
'1333234800'

1st of April 2012 UTC from epoch is 1333238400 but this above returns 1333234800 which is different by 1 hour.

So it looks like that strftime is taking my system time into account and applies a timezone shift somewhere. I thought datetime was purely naive?

How can I get around that? If possible avoiding to import other libraries unless standard. (I have portability concerns).

8
pythondatetimeutcepochstrftime
related: Converting datetime.date to UTC timestamp in Python – jfs
Am I the only one noting that you use octal literals in the numbers? – Fish Monitor
related Python issue: datetime.strftime('%s') should respect tzinfo – jfs
Newer Python 3.3+ has datetime.datetime.timestamp(datetime.datetime.utcnow()) – MarkHu
for the opposite operation go here: in-python-how-do-you-convert-seconds-since-epoch-to-a-datetime-object – MarkHu

8 Answers

469
votes

If you want to convert a python datetime to seconds since epoch you could do it explicitly:

>>> (datetime.datetime(2012,04,01,0,0) - datetime.datetime(1970,1,1)).total_seconds()
1333238400.0

In Python 3.3+ you can use timestamp() instead:

>>> datetime.datetime(2012,4,1,0,0).timestamp()
1333234800.0

Why you should not use datetime.strftime('%s')

Python doesn't actually support %s as an argument to strftime (if you check at http://docs.python.org/library/datetime.html#strftime-and-strptime-behavior it's not in the list), the only reason it's working is because Python is passing the information to your system's strftime, which uses your local timezone.

>>> datetime.datetime(2012,04,01,0,0).strftime('%s')
'1333234800'
104
votes

I had serious issues with Timezones and such. The way Python handles all that happen to be pretty confusing (to me). Things seem to be working fine using the calendar module (see links 1, 2, 3 and 4).

>>> import datetime
>>> import calendar
>>> aprilFirst=datetime.datetime(2012, 04, 01, 0, 0)
>>> calendar.timegm(aprilFirst.timetuple())
1333238400
37
votes
import time
from datetime import datetime
now = datetime.now()

time.mktime(now.timetuple())
16
votes
import time
from datetime import datetime
now = datetime.now()

# same as above except keeps microseconds
time.mktime(now.timetuple()) + now.microsecond * 1e-6

(Sorry, it wouldn't let me comment on existing answer)

7
votes

if you just need a timestamp in unix /epoch time, this one line works:

created_timestamp = int((datetime.datetime.now() - datetime.datetime(1970,1,1)).total_seconds())
>>> created_timestamp
1522942073L

and depends only on datetime works in python2 and python3

4
votes

For an explicit timezone-independent solution, use the pytz library.

import datetime
import pytz

pytz.utc.localize(datetime.datetime(2012,4,1,0,0), is_dst=False).timestamp()

Output (float): 1333238400.0

3
votes

This works in Python 2 and 3:

>>> import time
>>> import calendar
>>> calendar.timegm(time.gmtime())
1504917998

Just following the official docs... https://docs.python.org/2/library/time.html#module-time

-1
votes

In Python 3.7

Return a datetime corresponding to a date_string in one of the formats emitted by date.isoformat() and datetime.isoformat(). Specifically, this function supports strings in the format(s) YYYY-MM-DD[*HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]], where * can match any single character.

https://docs.python.org/3/library/datetime.html#datetime.datetime.fromisoformat