The shapefile used to compute the timezone is not maintained anymore.
I just faced the same issue today, and I am not sure how relevant my answer is after all this time, but I basically just wrote a Python function that does what you want. You can find it here.
https://github.com/cstich/gpstotz
Edit:
As mentioned in the comments I should also post code. The code is based on Eric Muller's shapefile of timezones, which you can get here - http://efele.net/maps/tz/world/.
Edit 2:
As it turns out shapefiles have a somewhat archaic definition of exterior and interior rings (basically exterior rings are using the right hand rule, while interior rings are using the left hand rule). In any case fiona seems to take care of that and I updated the code accordingly.
from rtree import index # requires libspatialindex-c3.deb
from shapely.geometry import Polygon
from shapely.geometry import Point
import os
import fiona
''' Read the world timezone shapefile '''
tzshpFN = os.path.join(os.path.dirname(__file__),
'resources/world/tz_world.shp')
''' Build the geo-index '''
idx = index.Index()
with fiona.open(tzshpFN) as shapes:
for i, shape in enumerate(shapes):
assert shape['geometry']['type'] == 'Polygon'
exterior = shape['geometry']['coordinates'][0]
interior = shape['geometry']['coordinates'][1:]
record = shape['properties']['TZID']
poly = Polygon(exterior, interior)
idx.insert(i, poly.bounds, obj=(i, record, poly))
def gpsToTimezone(lat, lon):
'''
For a pair of lat, lon coordiantes returns the appropriate timezone info.
If a point is on a timezone boundary, then this point is not within the
timezone as it is on the boundary. Does not deal with maritime points.
For a discussion of those see here:
http://efele.net/maps/tz/world/
@lat: latitude
@lon: longitude
@return: Timezone info string
'''
query = [n.object for n in idx.intersection((lon, lat, lon, lat),
objects=True)]
queryPoint = Point(lon, lat)
result = [q[1] for q in query
if q[2].contains(queryPoint)]
if len(result) > 0:
return result[0]
else:
return None
if __name__ == "__main__":
''' Tests '''
assert gpsToTimezone(0, 0) is None # In the ocean somewhere
assert gpsToTimezone(51.50, 0.12) == 'Europe/London'