Fix Python – How to preserve timezone when parsing date/time strings with strptime()?

Question

Asked By – victorhooi

I have a CSV dumpfile from a Blackberry IPD backup, created using IPDDump.
The date/time strings in here look something like this
(where EST is an Australian time-zone):

Tue Jun 22 07:46:22 EST 2010

I need to be able to parse this date in Python. At first, I tried to use the strptime() function from datettime.

>>> datetime.datetime.strptime('Tue Jun 22 12:10:20 2010 EST', '%a %b %d %H:%M:%S %Y %Z')

However, for some reason, the datetime object that comes back doesn’t seem to have any tzinfo associated with it.

I did read on this page that apparently datetime.strptime silently discards tzinfo, however, I checked the documentation, and I can’t find anything to that effect documented here.

Is there any way to get strptime() to play nicely with timezones?

Now we will see solution for issue: How to preserve timezone when parsing date/time strings with strptime()?


Answer

The datetime module documentation says:

Return a datetime corresponding to date_string, parsed according to format. This is equivalent to datetime(*(time.strptime(date_string, format)[0:6])).

See that [0:6]? That gets you (year, month, day, hour, minute, second). Nothing else. No mention of timezones.

Interestingly, [Win XP SP2, Python 2.6, 2.7] passing your example to time.strptime doesn’t work but if you strip off the ” %Z” and the ” EST” it does work. Also using “UTC” or “GMT” instead of “EST” works. “PST” and “MEZ” don’t work. Puzzling.

It’s worth noting this has been updated as of version 3.2 and the same documentation now also states the following:

When the %z directive is provided to the strptime() method, an aware datetime object will be produced. The tzinfo of the result will be set to a timezone instance.

Note that this doesn’t work with %Z, so the case is important. See the following example:

In [1]: from datetime import datetime

In [2]: start_time = datetime.strptime('2018-04-18-17-04-30-AEST','%Y-%m-%d-%H-%M-%S-%Z')

In [3]: print("TZ NAME: {tz}".format(tz=start_time.tzname()))
TZ NAME: None

In [4]: start_time = datetime.strptime('2018-04-18-17-04-30-+1000','%Y-%m-%d-%H-%M-%S-%z')

In [5]: print("TZ NAME: {tz}".format(tz=start_time.tzname()))
TZ NAME: UTC+10:00

This question is answered By – John Machin

This answer is collected from stackoverflow and reviewed by FixPython community admins, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0