This is a fork of tz-lookup module. It's been gently touched to enable client side (in browser) usage.

This is a little module that allows you to look up the current time zone of a location, given it's latitude and longitude. I wrote it because the existing Node module that does this (tzwhere) was far too slow to be useful in a production setting. This module attempts to ameliorate that.

To install:

npm install tz-lookup

To use:

const { tz, init } = require("tz-lookup");
await init(); // need to initialize the data
const tz = tz(42.7235, -73.6931));
assert(tz === "America/New_York")

Or you can use async version - init is done as needed:

const { tzAsync: tz } = require("tz-lookup");
const tz = async tz(42.7235, -73.6931));
assert(tz === "America/New_York")

Please take note of the following:

• The exported function call will throw an error if the latitude or longitude provided are out of bounds. Otherwise it will return an IANA timezone database string.
• The timezones returned by this module are approximate: since the timezone database is so large, lossy compression is necessary for fast lookups. In particular, the compression used may be of insufficient resolution for several very small timezones and favors country timezones over GMT offsets (and so may exaggerate the distance of territorial waters). However, the level of accuracy should be adequate for most purposes. (For example, this module is used by the Dark Sky API for global timezone lookups.)

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.

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 compressed database, simply run rebuild.sh.

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