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A library for working with the geography of timezones in JavaScript
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dbaron/tzmap.js
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# tzmap.js - Library for working with the geography of timezones in JavaScript # Written in 2011 by L. David Baron <dbaron@dbaron.org> # To the extent possible under law, the author(s) have dedicated all # copyright and related and neighboring rights to this software to the # public domain worldwide. This software is distributed without any # warranty. # # You should have received a copy of the CC0 Public Domain Dedication # along with this software. If not, see # <http://creativecommons.org/publicdomain/zero/1.0/>. This is tzmap.js, a library for working with the geography of time zones from JavaScript. This is a companion library to tz.js, providing the geography-related features. It is intended to support applications that want to map locations (latitude/longitude pairs) to time zone names and applications that want to draw maps of time zones. It incorporates data from http://efele.net/maps/tz/ , "A set of shapefiles for the TZ timezones", available under CC0. Files currently in the distribution are: pyshp/ The Python Shapefile Library (under its own license). shapefile-to-json.py Code to construct the JSON data needed by tzmap.js from the tzmap shapefiles. The library has the goal of providing these basic functions: (1) Map a (lat,lon) pair to zero or one timezones. (2) Get the shape outlines for a given timezone to draw the boundaries of a TZ database timezone. (3) Merge the shape outlines for adjacent timezones in order to draw the boundaries of a set of adjacent timezones (eliminating edges that were between two merged zones). This allows drawing maps showing the timezone lines at a given point in time, or maps showing the regions that have a summer time change within a specific period (perhaps coded by the day they change). This has the following implications for data structures: For (1), we want a quick test that allows rapidly eliminating most timezones; this is done by storing the N/E/S/W edges of the smallest rectangle enclosing all of the zone's polygons. For (3), we want each polygon for the zone to be stored as a list of (segment, direction-on-segment) pairs, and each segment to know which one or two zones it separates. Build instructions: * Download the tz_world_mp.zip file from http://efele.net/maps/tz/world/ and place it in ../tzmap/ (or elsewhere, and adjust the path at the top of shapefile-to-json.py) * Run |make| to generate the output in output/ Note that https://github.com/dbaron/timezone-map is a project that uses this library (and the one I wrote it for). It's possible that some code in that repository might make sense being moved in this library.
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