How to get system timezone setting and pass it to pytz.timezone?

We can use time.tzname get a local timezone name, but that name is not compatible with pytz.timezone.

In fact, the name returned by time.tzname is ambiguous. This method returns ('CST', 'CST') in my system, but ‘CST’ can indicate four timezones:

• Central Time Zone (North America) – observed in North America’s Central Time Zone
• China Standard Time
• Chungyuan Standard Time – the term “Chungyuan Standard Time” is now rarely in use in Taiwan
• Australian Central Standard Time (ACST)

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

tzlocal module returns pytz tzinfo’s object corresponding to the local timezone:

import time
from datetime import datetime

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

# get local timezone    
local_tz = get_localzone() 

# test it
# utc_now, now = datetime.utcnow(), datetime.now()
ts = time.time()
utc_now, now = datetime.utcfromtimestamp(ts), datetime.fromtimestamp(ts)

local_now = utc_now.replace(tzinfo=pytz.utc).astimezone(local_tz) # utc -> local
assert local_now.replace(tzinfo=None) == now

It works even during daylight savings time transitions when local time may be ambiguous.

local_tz also works for past dates even if utc offset for the local timezone was different at the time. dateutil.tz.tzlocal()-based solution fails in this case e.g., in Europe/Moscow timezone (example from 2013):

>>> import os, time
>>> os.environ['TZ'] = 'Europe/Moscow'
>>> time.tzset()
>>> from datetime import datetime
>>> from dateutil.tz import tzlocal
>>> from tzlocal import get_localzone
>>> dateutil_tz = tzlocal()
>>> tzlocal_tz = get_localzone()
>>> datetime.fromtimestamp(0, dateutil_tz)                              
datetime.datetime(1970, 1, 1, 4, 0, tzinfo=tzlocal())
>>> datetime.fromtimestamp(0, tzlocal_tz)
datetime.datetime(1970, 1, 1, 3, 0, tzinfo=<DstTzInfo 'Europe/Moscow' MSK+3:00:00 STD>)

dateutil returns wrong UTC+4 offset instead of the correct UTC+3 on 1970-01-01.

For those bumping into this in 2017 dateutil.tz.tzlocal() is still broken. The above example works now because the current utf offset is UTC+3 in Moscow (that by accident is equal to the utc offset from 1970). To demonstrate the error we can choose a date when utc offset is UTC+4:

>>> import os, time
>>> os.environ['TZ'] = 'Europe/Moscow'
>>> time.tzset()
>>> from datetime import datetime
>>> from dateutil.tz import tzlocal
>>> from tzlocal import get_localzone
>>> dateutil_tz = tzlocal()
>>> tzlocal_tz = get_localzone()
>>> ts = datetime(2014, 6,1).timestamp() # get date in 2014 when gmtoff=14400 in Moscow
>>> datetime.fromtimestamp(ts, dateutil_tz)
datetime.datetime(2014, 5, 31, 23, 0, tzinfo=tzlocal())
>>> datetime.fromtimestamp(ts, tzlocal_tz)
datetime.datetime(2014, 6, 1, 0, 0, tzinfo=<DstTzInfo 'Europe/Moscow' MSK+4:00:00 STD>)

dateutil returns wrong UTC+3 offset instead of the correct UTC+4 on 2014-06-01.

Method 2

Use the tzlocal function from the python-dateutil package:

from dateutil.tz import tzlocal

localtimezone = tzlocal()

Internally, this is a class that uses time.timezone and time.altzone (switching based on time.daylight), but creates a suitable timezone object from that.

You use this instead of a pytz timezone.

The alternative is to read the currently configured timezone from the operating system instead, but this differs widely from OS to OS. On Mac OS X you need to read the output of systemsetup -gettimezone:

$ systemsetup -gettimezone
Time Zone: Europe/Copenhagen

On Debian and Ubuntu systems, you can read /etc/timezone:

$ cat /etc/timezone
Europe/Oslo

On RedHat and direved systems, you’ll need to read it from /etc/sysconfig/clock:

$ grep ZONE /etc/sysconfig/clock
ZONE="Europe/Oslo"

Method 3

Since Python 3.6, you can simply run naive_datetime.astimezone() and system time zone will be added to naive_datetime object.

If called without arguments (or with tz=None) the system local timezone is assumed for the target timezone. The .tzinfo attribute of the converted datetime instance will be set to an instance of timezone with the zone name and offset obtained from the OS.

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

Example:

>>> import datetime
>>> datetime.datetime.now().astimezone().isoformat(timespec='minutes')
'2018-10-02T13:09+03:00'

Method 4

A very simple method to solve this question:

import time

def localTzname():
    offsetHour = time.timezone / 3600
    return 'Etc/GMT%+d' % offsetHour

Update: @MartijnPieters said ‘This won’t work with DST / summertime.’ So how about this version?

import time

def localTzname():
    if time.daylight:
        offsetHour = time.altzone / 3600
    else:
        offsetHour = time.timezone / 3600
    return 'Etc/GMT%+d' % offsetHour

Method 5

i don’t know if this is useful for you or not, but i think it answers your more general problem:

if you have a date that is in an ambiguous timezone, like CST, simple-date (python 3.2+ only, sorry) can automate the search, and allows you to do things like prefer certain countries.

for example:

>>> SimpleDate('2013-07-04 18:53 CST')
Traceback [...
simpledate.AmbiguousTimezone: 3 distinct timezones found: <DstTzInfo 'Australia/Broken_Hill' CST+9:30:00 STD>; <DstTzInfo 'America/Regina' LMT-1 day, 17:01:00 STD>; <DstTzInfo 'Asia/Harbin' LMT+8:27:00 STD> (timezones=('CST',), datetime=datetime.datetime(2013, 7, 4, 18, 53), is_dst=False, country=None, unsafe=False)
>>> SimpleDate('2013-07-04 18:53 CST', country='CN')
SimpleDate('2013-07-04 18:53 CST')
>>> SimpleDate('2013-07-04 18:53 CST', country='CN').utc
SimpleDate('2013-07-04 10:53 UTC', tz='UTC')

note how, by specifying a country you reduce the range of possible values sufficiently to allow conversion to UTC.

it’s implemented by doing a search over the timezones in PyTZ:

>>> SimpleDate('2013-07-04 18:53 CST', country='CN', debug=True)
...
PyTzFactory: Have country code CN
PyTzFactory: Country code CN has 5 timezones
PyTzFactory: Expanded country codes to 5 timezones
PyTzFactory: Expanding ('CST',)
PyTzFactory: Name lookup failed for CST
PyTzFactory: Found CST using Asia/Shanghai
PyTzFactory: Found CST using Asia/Harbin
PyTzFactory: Found CST using Asia/Chongqing
PyTzFactory: Found CST using Asia/Urumqi
PyTzFactory: Found CST using Asia/Kashgar
PyTzFactory: Expanded timezone to 5 timezones
PyTzFactory: New offset 8:00:00 for Asia/Shanghai
PyTzFactory: Known offset 8:00:00 for Asia/Harbin
PyTzFactory: Known offset 8:00:00 for Asia/Chongqing
PyTzFactory: Known offset 8:00:00 for Asia/Urumqi
PyTzFactory: Known offset 8:00:00 for Asia/Kashgar
PyTzFactory: Have 1 distinct timezone(s)
PyTzFactory: Found Asia/Shanghai
...
SimpleDate('2013-07-04 18:53 CST')

finally, to answer the question asked directly, it also wraps tzlocal, as mentioned in another answer here, so will automatically do what you expect if you don’t give a timezone. for example, i live in chile, so

>>> SimpleDate()
SimpleDate('2013-07-04 19:21:25.757222 CLT', tz='America/Santiago')
>>> SimpleDate().tzinfo
<DstTzInfo 'America/Santiago' CLT-1 day, 20:00:00 STD>

gives my locale’s timezone (ambiguous or not).

Method 6

import pytz

say you have list of utc DateTime values in OBJ list object.

tz=pytz.timezone('Asia/Singapore')

find below url to get respective timezone positional string parameter
Is there a list of Pytz Timezones?

Now our tz is object having singapore Time

result=[]
for i in OBJ:
    i=i+tz.utcoffset(i)
    result.append(i)

result list object has DateTime value of your respective timezone

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0