Get a user's timezone on app engine based off of the Google Maps Time Zone API

omg_timezone.py

import time
import json

from pytz.gae import pytz
from google.appengine.api import urlfetch

#: Preset object for America/New_York
EasternTz = pytz.timezone('America/New_York')

def user_timezone_from_latlong(lat_long=None):
    """Fetches a user's time zone based on their lat/long using the google maps time zone api

    See https://developers.google.com/maps/documentation/timezone/intro
    
    Example::

        >>> import webapp2
        >>> lat_long = webapp2.get_request().headers.get('X-Appengine-Citylatlong')
        >>> tz = user_timezone_from_latlong(lat_long)
        >>> print tz.tzname()

    :param str lat_long: User's lat/long. Usually from the request header X-Appengine-Citylatlong
    """
    if lat_long is None:
        return EasternTz
    unix_time = int(time.time())
    url = "https://maps.googleapis.com/maps/api/timezone/json" \
          "?location={lat_long}&timestamp={unix_time}&key={token}"
    url = url.format(lat_long=lat_long, unix_time=unix_time,
                     token=config.google_server_application_api_key)
    response = urlfetch.fetch(url)
    if response.status_code >= 400:
        raise Exception("Error fetching Time Zone info for {}: {}".format(
            lat_long, response.content
        ))
    zoneinfo = json.loads(response.content)
    if zoneinfo['status'] != "OK":
        raise Exception("{}".format(zoneinfo['error_message']))
    return pytz.timezone(zoneinfo.get('timeZoneId'))