Automatic timezone detection based on the user's browser for Django

django_auto_tz.py

# Inspiration from here: https://tutti.me/post/5453/
# Or you can use a library like:
#   - https://github.com/adamcharnock/django-tz-detect (last updated 2019)
#   - https://github.com/Miserlou/django-easy-timezones (last updated 2016)
#   - https://github.com/jamesmfriedman/django-easytz (last updated 2015)
# Or guess TZ using visitors IP GEOIP: https://codereview.stackexchange.com/questions/161261/set-time-zone-from-cookie

# settings.py

 TEMPLATES = [{
    ...
    'OPTIONS': {
        'context_processors': [
            ...
            'myapp.context_processors.timezone_processor',
        ],
    },
 }]
 

 from django.utils import timezone

 def timezone_processor(request):
     # look for a cookie that we expect to have the timezone
     tz = request.COOKIES.get('local_timezone', None)
     if tz:
         tz_int = int(tz) # cast to int
         # here we decide what will prefix timezone number
         # the output of tz_str will be something like: 
         #                Etc/GMT+1, GMT+0, Etc/GMT-2
         if tz_int >= 0:
             tz_str = 'Etc/GMT+'+tz
         else:
             tz_str = 'Etc/GMT'+tz
         # this forces timezone
         timezone.activate(tz_str)
     # Now we tell the template that we have a timezone
     return {'local_timezone': tz}
 

# templates/base.html

...
{% if not local_timezone %}
    <script>
        document.cookie = 'local_timezone=" + (new Date().getTimezoneOffset() / 60);
    </script>
{% endif %}