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 (~71KB) 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

Timezone data is sourced from Evan Siroky's timezone-boundary-builder. The database was last updated on 6 Jan 2019.

To regenerate the library's database yourself, you will need to install GDAL:

$ brew install gdal # on Mac OS X
$ sudo apt install gdal-bin # on Ubuntu

Then, simply execute rebuild.sh. Expect it to take 10-30 minutes, depending on your network connection and CPU.

License

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