Getting Timezone using Intl API doesn't work in Firefox:

javascript firefox internationalization timezone ecmascript-intl
mikemaccana picture mikemaccana · Jun 13, 2016 · Viewed 14.9k times · Source

I am using the Intl API. In Chrome:

 Intl.DateTimeFormat().resolved.timeZone

Returns "Europe/London"

In Firefox this return undefined, even though Firefox supports Intl.

How can I get a timezone with Firefox?

Answer

Matt Johnson-Pint picture Matt Johnson-Pint · Jun 13, 2016

Technically, the more correct incantation is:

Intl.DateTimeFormat().resolvedOptions().timeZone

Unfortunately, not all implementations currently support the time zone features of the Intl API. So while this will return a valid IANA time zone in Chrome, it won't yet do that in FireFox and several other browsers.

The kangax Intl compatibility table shows this feature as a sub-item under the DateTimeFormat object labeled resolvedOptions().timeZone defaults to the host environment.

See the following FireFox work items:

  • Bug 1158733 - Detect system timezone from Javascript Internationalization API
  • Bug 895737 - DateTimeFormat doesn't track current time zone
  • Bug 837961 - Add support for IANA time zone names to internationalization API

In the meantime, there are two viable alternatives:

  • jsTimeZoneDetect - which is focused soley on the task of time zone guessing.
  • moment-timezone - which is an add-on to the popular moment.js library, and contains an API moment.tz.guess() to try to guess the user's time zone.

Note that both of these will internally try to use the Intl API if it is available and functioning, before trying additional guessing algorithms.

Also note that the best practice is to never rely solely on time zone detection / guessing, but rather to use it to select a sensible default value from a time zone picker control. Always give the user some way to choose their desired time zone. This is important, as the time zone they presently have their computer set to may or may not be the time zone they'd like to use within your application. For example, it's common for web-based calendaring software (such as Google Calendar, or Outlook.com) to allow the user to set a time zone in their user profile.

Related questions

JavaScript open in a new window, not tab

I have a select box that calls window.open(url) when an item is selected. Firefox will open the page in a new tab by default. However, I would like the page to open in a new window, not a …

Read More
How can I tell if a DOM element is visible in the current viewport?

Is there an efficient way to tell if a DOM element (in an HTML document) is currently visible (appears in the viewport)? (The question refers to Firefox.)

Read More
Get image data url in JavaScript?

I have a regular HTML page with some images (just regular <img /> HTML tags). I'd like to get their content, base64 encoded preferably, without the need to redownload the image (ie. it's already loaded by the browser, so …

Read More