getTimezoneOffset

getTimezoneOffset is a tiny library ( less than 1k ) for getting timezone offsets.

It returns the timezone offset in minutes for any IANA timezone name for any date in the past, present and future.

It runs in any browsers or on the server, it's very small, very fast and has no dependencies[^1]

Example

var now = new Date();
getTimezoneOffset( 'America/New_York', now ); // returns 300
getTimezoneOffset( 'Antarctica/Davis', now ); // return -420

How it works

getTimezoneOffset is tiny and fast because it ships without a database of timezones, using the tz database of the underlying operating system via the global Intl object.

Internationalization was introduced in 2012; Engine support is tracked here , but boils down to;

• Node: v4+
• Bun, Deno and other javascript runtimes
• All browsers

Tests

The tests will validate the library functionality and the javascript engine's implementation of Intl.DateTimeFormat ( and the operating systems tzinfo database ).

To test in node

npm test

To test in a browser

npm run test:browser

Then open test.html in a browser and view the console output.

Troubleshooting

[^1]: If you are running getTimezoneOffset on the server and using alpine or other ultra minimal docker image without a timezone database, you need to install the tzdata package. Most docker images, including the "slim" images publishd by node already include tzdata.

Results for locations that experience daylight saving change throughout the year Results for locations that [https://data.iana.org/time-zones/tzdb/NEWS](have moved timezone) may vary as the tz database is modified. This sometimes includes retrospective changes.