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This is a Go package which maps a (lat, long) to a timezone. My motivation was figuring out the UTC time of a JPG with EXIF metadata containing GPS coordinates and local time, but no timezone offset. This is a surprising number of photos. I built this to improve sorting in Camlistore, especially when photos are intermixed with tweets, checkins, etc, but it should be generally applicable. See docs at http://godoc.org/github.com/bradfitz/latlong It tries to have a small binary size (~360 KB), low memory footprint (~1 MB), and incredibly fast lookups (~0.5 microseconds). It does not try to be perfectly accurate when very close to borders. To rebuild the data files, see the Makefile (or just run make). You'll need the data files unzip to the "world" directory. Some background: https://plus.google.com/u/0/+BradFitzpatrick/posts/XVyy1bAzkZd Another image of the underlying data structure: http://i.imgur.com/Rt8bLSD.png ... the tile borders are only there for debugging, to show areas with only one timezone. Tiles without borders around them still work; at that level, the small possible bitmap is used for lookup.

Formed in 2009, the Archive Team (not to be confused with the archive.org Archive-It Team) is a rogue archivist collective dedicated to saving copies of rapidly dying or deleted websites for the sake of history and digital heritage. The group is 100% composed of volunteers and interested parties, and has expanded into a large amount of related projects for saving online and digital history.
