Get the Olson TZ name for the local timezone?

This is kind of cheating, I know, but getting from '/etc/localtime' doesn't work for you? Like following:

>>>  import os>>> '/'.join(os.readlink('/etc/localtime').split('/')[-2:])'Australia/Sydney'

Hope it helps.

Edit: I liked @A.H.'s idea, in case '/etc/localtime' isn't a symlink. Translating that into Python:

#!/usr/bin/env pythonfrom hashlib import sha224import osdef get_current_olsonname():    tzfile = open('/etc/localtime')    tzfile_digest = sha224(tzfile.read()).hexdigest()    tzfile.close()    for root, dirs, filenames in os.walk("/usr/share/zoneinfo/"):        for filename in filenames:            fullname = os.path.join(root, filename)            f = open(fullname)            digest = sha224(f.read()).hexdigest()            if digest == tzfile_digest:                return '/'.join((fullname.split('/'))[-2:])            f.close()        return Noneif __name__ == '__main__':    print get_current_olsonname()

I think best bet is to go thru all pytz timezones and check which one matches local timezone, each pytz timezone object contains info about utcoffset and tzname like CDT, EST, same info about local time can be obtained from time.timezone/altzone and time.tzname, and I think that is enough to correctly match local timezone in pytz database e.g.

import timeimport pytzimport datetimelocal_names = []if time.daylight:    local_offset = time.altzone    localtz = time.tzname[1]else:    local_offset = time.timezone    localtz = time.tzname[0]local_offset = datetime.timedelta(seconds=-local_offset)for name in pytz.all_timezones:    timezone = pytz.timezone(name)    if not hasattr(timezone, '_tzinfos'):        continue#skip, if some timezone doesn't have info    # go thru tzinfo and see if short name like EDT and offset matches    for (utcoffset, daylight, tzname), _ in timezone._tzinfos.iteritems():        if utcoffset == local_offset and tzname == localtz:            local_names.append(name)print local_names

output:

['America/Atikokan', 'America/Bahia_Banderas', 'America/Bahia_Banderas', 'America/Belize', 'America/Cambridge_Bay', 'America/Cancun', 'America/Chicago', 'America/Chihuahua', 'America/Coral_Harbour', 'America/Costa_Rica', 'America/El_Salvador', 'America/Fort_Wayne', 'America/Guatemala', 'America/Indiana/Indianapolis', 'America/Indiana/Knox', 'America/Indiana/Marengo', 'America/Indiana/Marengo', 'America/Indiana/Petersburg', 'America/Indiana/Tell_City', 'America/Indiana/Vevay', 'America/Indiana/Vincennes', 'America/Indiana/Winamac', 'America/Indianapolis', 'America/Iqaluit', 'America/Kentucky/Louisville', 'America/Kentucky/Louisville', 'America/Kentucky/Monticello', 'America/Knox_IN', 'America/Louisville', 'America/Louisville', 'America/Managua', 'America/Matamoros', 'America/Menominee', 'America/Merida', 'America/Mexico_City', 'America/Monterrey', 'America/North_Dakota/Beulah', 'America/North_Dakota/Center', 'America/North_Dakota/New_Salem', 'America/Ojinaga', 'America/Pangnirtung', 'America/Rainy_River', 'America/Rankin_Inlet', 'America/Resolute', 'America/Resolute', 'America/Tegucigalpa', 'America/Winnipeg', 'CST6CDT', 'Canada/Central', 'Mexico/General', 'US/Central', 'US/East-Indiana', 'US/Indiana-Starke']

In production you can create such a mapping beforehand and save it instead of iterating always.

Testing script after changing timezone:

$ export TZ='Australia/Sydney'
$ python get_tz_names.py
['Antarctica/Macquarie', 'Australia/ACT', 'Australia/Brisbane', 'Australia/Canberra', 'Australia/Currie', 'Australia/Hobart', 'Australia/Lindeman', 'Australia/Melbourne', 'Australia/NSW', 'Australia/Queensland', 'Australia/Sydney', 'Australia/Tasmania', 'Australia/Victoria']

One problem is that there are multiple "pretty names" , like "Australia/Sydney" , which point to the same time zone (e.g. CST).

So you will need to get all the possible names for the local time zone, and then select the name you like.

e.g.: for Australia, there are 5 time zones, but way more time zone identifiers:

     "Australia/Lord_Howe", "Australia/Hobart", "Australia/Currie",      "Australia/Melbourne", "Australia/Sydney", "Australia/Broken_Hill",      "Australia/Brisbane", "Australia/Lindeman", "Australia/Adelaide",      "Australia/Darwin", "Australia/Perth", "Australia/Eucla"

you should check if there is a library which wraps TZinfo , to handle the time zone API.

e.g.: for Python, check the pytz library:

http://pytz.sourceforge.net/

and

http://pypi.python.org/pypi/pytz/

in Python you can do:

from pytz import timezoneimport pytzIn [56]: pytz.country_timezones('AU')Out[56]: [u'Australia/Lord_Howe', u'Australia/Hobart', u'Australia/Currie', u'Australia/Melbourne', u'Australia/Sydney', u'Australia/Broken_Hill', u'Australia/Brisbane', u'Australia/Lindeman', u'Australia/Adelaide', u'Australia/Darwin', u'Australia/Perth', u'Australia/Eucla']

but the API for Python seems to be pretty limited, e.g. it doesn't seem to have a call like Ruby's all_linked_zone_names -- which can find all the synonym names for a given time zone.