#Introduction#

Eric Muller (http://efele.net/maps/tz/world/) originally created the awesome Shape file of time zones. This essentially allows you to look up a time zone based on geographic coordinates (lat/long).

Why would you want to do this?

• You can convert times/dates displayed on your website in the users local time
• You can use it as part of a validation scheme (make sure the users computer time zone is the same as you expect, and they are not using a proxy or VPN)
• Notify a user if their local time zone setting may be incorrect
• Show a cool map of what the world looks like with time zone boundaries instead of political ones.

I decided to fork his work so that I can keep the data up to date on my own cycle. As well, I have plans to turn this into a shared library that can be used elsewhere.

#The Data# The shape file contains just one field. The "name" of the time zone as found in IANA's Time Zone Database (http://www.iana.org/time-zones). This means that you will have to work with strings such as "America/Toronto" or "Australia/Sydney".

It's up to you to then convert that time zone name into a proper numerical offset from UTC. This can usually be done with your language of choice and your operating systems local version of the zoneinfo database.

##Update Frequency## I try to update the data as soon as IANA does. They announce updates via their mailing list, and versions are numbered based on the year. So for example: 2014b would be the second version released in 2014. It's usually updated around once a month.

#Gimme my shapefile!# You can find the latest version of the shape file in this repo (in the output subdirectory):

• World: https://github.com/blakecrosby/tz-map/tree/master/world/output
  • tz_world.* contains individual polygons for every region. (1 record per region)
  • tz_world_mp.* contains multipolygons for every region. (1 record per time zone)
  • tz_world_robinson is the tz_world shape in Robinson Projection (for display purposes)
• Antarctica: https://github.com/blakecrosby/tz-map/tree/master/antarctica/output
  • This shapefile contains POINTS and not areas. This is because the region is dotted by research stations and not actual areas. Keep this in mind when trying to run a Postgis query against this data set.

#Contact# Please feel free to contact me (me@blakecrosby.com) if you have any questions. I encourage pull requests to update the database if you find any errors.