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tz-lookup

tz-lookup

This is a little Javascript library that allows you to look up the time zone of a location given its latitude and longitude. It works in both the browser and in Node.JS, and is very fast and lightweight (~121KB) given what it does. We use it in production for The Dark Sky API.

Usage

To install:

npm install tz-lookup

Node.JS usage:

var tzlookup = require("tz-lookup");
console.log(tzlookup(42.7235, -73.6931)); // prints "America/New_York" 

Browser usage:

<script src="tz.js"></script>
<script>
alert(tzlookup(42.7235, -73.6931)); // alerts "America/New_York"
</script> 

Please take note of the following:

  • The exported function call will throw an error if the latitude or longitude provided are NaN or out of bounds. Otherwise, it will never throw an error and will always return an IANA timezone database string. (Barring bugs.)

  • The timezones returned by this module are approximate: since the timezone database is so large, lossy compression is necessary for a small footprint and fast lookups. Expect errors near timezone borders far away from populated areas. However, for most use-cases, this module's accuracy should be adequate.

    If you find a real-world case where this module's accuracy is inadequate, please open an issue (or, better yet, submit a pull request with a failing test) and I'll see what I can do to increase the accuracy for you.

Sources

Versions prior to 6.0.7 used timezone data from Eric Muller's excellent TZ timezone maps. As of 6.0.7, we now use timezone data from @evansiroky's also-excellent timezone-boundary-builder. To regenerate the library, simply run rebuild.sh. The timezone database was last updated on 8 Mar 2017.

License

To the extent possible by law, The Dark Sky Company, LLC has waived all copyright and related or neighboring rights to this library.