pytzwhere is a Python library to lookup the timezone for a given lat/lng entirely offline.
It is a port from https://github.com/mattbornski/tzwhere with a few improvements. The underlying timezone data is based on work done by Eric Muller
If used as a library, basic usage is as follows:
>>> from tzwhere import tzwhere
>>> tz = tzwhere.tzwhere()
>>> print tz.tzNameAt(35.29, -89.66)
America/Chicago
If you have shapely installed, you can use that library to speed up things by a factor of hundreds. Initialization takes considerably longer (about 20 seconds longer) though. Only really makes sense if you have a lot of points to look up.
>>> tz = tzwhere.tzwhere(shapely=True)
>>> print tz.tzNameAt(35.29, -89.66)
America/Chicago
The polygons used for building the timezones are based on VMAP0. Sometimes points are outside a VMAP0 polygon, but are clearly within a certain timezone (see also this discussion). As a somewhat 'hacky' workaround you can tell the library to return the closest timezone if it doesn't find a proper timezone. Only works if the point is reasonably close to a valid timezone in the first place. This costs you another 80MB of RAM or so. You need to use shapely for this.
>>> tz = tzwhere.tzwhere(shapely=True, forceTZ=True)
>>> # This is on the shore of Lake Michigan
>>> tz.tzNameAt(40.7271, -73.98)
>>> tz.tzNameAt(40.7271, -73.98, forceTZ=True)
'America/New_York'
>>> tz.tzNameAt(50.1536, -5.030)
>>> # This is slightly off the shore of Cornwall
>>> tz.tzNameAt(50.1536, -5.030, forceTZ=True)
>>> 'Europe/London'
>>> # Far off the coast of Cornwall
>>> tz.tzNameAt(50.26, -9.051, forceTZ=True)
The module can also be run as a script, which offers some other possibilities including producing various input files. Instructions and usage information can be seen by running:
tzwhere.py --help
Dependencies (all optional):
-
docopt- if you want to usetzwhere.pyas a script (e.g. as shown above). -
numpy- if you want to save about 200MB of RAM. -
shapely- if you want to speed up things by a factor of hundreds