How to get a time zone from a location using latitude and longitude coordinates?

Question

Given the latitude and longitude of a location, how does one know what time zone is in effect in that location?

In most cases, we are looking for an IANA/Olson time z

Answer 1

It's indeed important to recognize that this a more complicated problem than most would suspect. In practice many of us are also willing to accept a working set of code that works for "as many cases as possible", where at least its fatal issues can be identified and minimized collectively. So I post this with all of that and the spirit of the OP in mind. Finally, for practical value to others who are trying to convert GPS to timezone with the end goal of having a location-sensitive time object (and more importantly to help advance the quality of average implementations with time objects that follow from this wiki) here is what I generated in Python (please feel free to edit):

import pytz
from datetime import datetime
from tzwhere import tzwhere

def timezoned_unixtime(latitude, longitude, dt):
    tzw = tzwhere.tzwhere()
    timezone_str = tzw.tzNameAt(latitude, longitude)
    timezone = pytz.timezone(timezone_str)
    timezone_aware_datetime = timezone.localize(dt, is_dst=None)
    unix_time = (timezone_aware_datetime - datetime(1970, 1, 1, tzinfo=pytz.utc)).total_seconds()
    return unix_time

dt = datetime(year=2017, month=1, day=17, hour=12, minute=0, second=0)
print timezoned_unixtime(latitude=40.747854, longitude=-74.004733, dt=dt)