How do I print a Python datetime in the local time

Question

Let's say I have a variable t that's set to this:

datetime.datetime(2009, 7, 10, 18, 44, 59, 193982, tzinfo=<UTC>)

If I say str(t), i get:

'2009-07-10 18:44:59.193982+00:00'

How can I get a similar string, except printed in the local timezone rather than UTC?

Answer 1

Think your should look around: datetime.astimezone()

http://docs.python.org/library/datetime.html#datetime.datetime.astimezone

Also see pytz module - it's quite easy to use -- as example:

eastern = timezone('US/Eastern')

http://pytz.sourceforge.net/

Example:

from datetime import datetime
import pytz
from tzlocal import get_localzone # $ pip install tzlocal

utc_dt = datetime(2009, 7, 10, 18, 44, 59, 193982, tzinfo=pytz.utc)
print(utc_dt.astimezone(get_localzone())) # print local time
# -> 2009-07-10 14:44:59.193982-04:00

Answer 2

As of python 3.2, using only standard library functions:

u_tm = datetime.datetime.utcfromtimestamp(0)
l_tm = datetime.datetime.fromtimestamp(0)
l_tz = datetime.timezone(l_tm - u_tm)

t = datetime.datetime(2009, 7, 10, 18, 44, 59, 193982, tzinfo=l_tz)
str(t)
'2009-07-10 18:44:59.193982-07:00'

Just need to use l_tm - u_tm or u_tm - l_tm depending whether you want to show as + or - hours from UTC. I am in MST, which is where the -07 comes from. Smarter code should be able to figure out which way to subtract.

And only need to calculate the local timezone once. That is not going to change. At least until you switch from/to Daylight time.

Answer 3

I believe the best way to do this is to use the LocalTimezone class defined in the datetime.tzinfo documentation (goto http://docs.python.org/library/datetime.html#tzinfo-objects and scroll down to the "Example tzinfo classes" section):

Assuming Local is an instance of LocalTimezone

t = datetime.datetime(2009, 7, 10, 18, 44, 59, 193982, tzinfo=utc)
local_t = t.astimezone(Local)

then str(local_t) gives:

'2009-07-11 04:44:59.193982+10:00'

which is what you want.

(Note: this may look weird to you because I'm in New South Wales, Australia which is 10 or 11 hours ahead of UTC)

Answer 4

I use this function datetime_to_local_timezone(), which seems overly convoluted but I found no simpler version of a function that converts a datetime instance to the local time zone, as configured in the operating system, with the UTC offset that was in effect at that time:

import time, datetime

def datetime_to_local_timezone(dt):
    epoch = dt.timestamp() # Get POSIX timestamp of the specified datetime.
    st_time = time.localtime(epoch) #  Get struct_time for the timestamp. This will be created using the system's locale and it's time zone information.
    tz = datetime.timezone(datetime.timedelta(seconds = st_time.tm_gmtoff)) # Create a timezone object with the computed offset in the struct_time.

    return dt.astimezone(tz) # Move the datetime instance to the new time zone.

utc = datetime.timezone(datetime.timedelta())
dt1 = datetime.datetime(2009, 7, 10, 18, 44, 59, 193982, utc) # DST was in effect
dt2 = datetime.datetime(2009, 1, 10, 18, 44, 59, 193982, utc) # DST was not in effect

print(dt1)
print(datetime_to_local_timezone(dt1))

print(dt2)
print(datetime_to_local_timezone(dt2))

This example prints four dates. For two moments in time, one in January and one in July 2009, each, it prints the timestamp once in UTC and once in the local time zone. Here, where CET (UTC+01:00) is used in the winter and CEST (UTC+02:00) is used in the summer, it prints the following:

2009-07-10 18:44:59.193982+00:00
2009-07-10 20:44:59.193982+02:00

2009-01-10 18:44:59.193982+00:00
2009-01-10 19:44:59.193982+01:00

Answer 5

I wrote something like this the other day:

import time, datetime
def nowString():
    # we want something like '2007-10-18 14:00+0100'
    mytz="%+4.4d" % (time.timezone / -(60*60) * 100) # time.timezone counts westwards!
    dt  = datetime.datetime.now()
    dts = dt.strftime('%Y-%m-%d %H:%M')  # %Z (timezone) would be empty
    nowstring="%s%s" % (dts,mytz)
    return nowstring

So the interesting part for you is probably the line starting with "mytz=...". time.timezone returns the local timezone, albeit with opposite sign compared to UTC. So it says "-3600" to express UTC+1.

Despite its ignorance towards Daylight Saving Time (DST, see comment), I'm leaving this in for people fiddling around with time.timezone.