如何获取系统时区设置并将其传递给 pytz.timezone?

我们可以使用 time.tzname获取本地时区名称,但该名称与 pytz.timezone不兼容。

事实上,time.tzname返回的名称是模棱两可的。这个方法在我的系统中返回 ('CST', 'CST'),但是“ CST”可以指示四个时区:

  • 中央时区(北美洲)-在北美洲的中央时区观察
  • 中国标准时间
  • 中原标准时间-“中原标准时间”一词现在在台湾很少使用
  • 澳大利亚中央标准时间
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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"

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

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.

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).

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

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'