Intl.DateTimeFormat (ESNext)

A spec-compliant polyfill for Intl.DateTimeFormat fully tested by the official ECMAScript Conformance test suite

size

caution

Right now we only support Gregorian calendar in this polyfill. Therefore we recommend setting calendar: 'gregory' in your options to be safe.

caution

Right now this polyfill supports daylight transition until 2038 due to Year 2038 problem.

Features#

Installation#

npm
yarn

npm i @formatjs/intl-datetimeformat

Requirements#

This package requires the following capabilities:

Usage#

Simple#

import '@formatjs/intl-datetimeformat/polyfill'
import '@formatjs/intl-datetimeformat/locale-data/en' // locale-data for en
import '@formatjs/intl-datetimeformat/add-all-tz' // Add ALL tz data

Dynamic import + capability detection#

import {shouldPolyfill} from '@formatjs/intl-datetimeformat/should-polyfill'
async function polyfill(locale: string) {
  if (shouldPolyfill()) {
    // Load the polyfill 1st BEFORE loading data
    await import('@formatjs/intl-datetimeformat/polyfill')
  }

  if (Intl.DateTimeFormat.polyfilled) {
    // Parallelize CLDR data loading
    const dataPolyfills = [import('@formatjs/intl-datetimeformat/add-all-tz')]

    switch (locale) {
      default:
        dataPolyfills.push(
          import('@formatjs/intl-datetimeformat/locale-data/en')
        )
        break
      case 'fr':
        dataPolyfills.push(
          import('@formatjs/intl-datetimeformat/locale-data/fr')
        )
        break
    }
    await Promise.all(dataPolyfills)
  }
}

Adding IANA Timezone Database#

We provide 2 pre-processed IANA Timezone:

Full: contains ALL Timezone from IANA database#

import '@formatjs/intl-datetimeformat/polyfill'
import '@formatjs/intl-datetimeformat/add-all-tz'

Golden: contains popular set of timezones from IANA database#

import '@formatjs/intl-datetimeformat/polyfill'
import '@formatjs/intl-datetimeformat/add-golden-tz'

Default Timezone#

Since JS Engines do not expose default timezone, there's currently no way for us to detect local timezone that a browser is in. Therefore, the default timezone in this polyfill is UTC.

You can change this by either calling __setDefaultTimeZone or always explicitly pass in timeZone option for accurate date time calculation.

Since __setDefaultTimeZone is not in the spec, you should make sure to check for its existence before calling it & after tz data has been loaded, e.g:

import '@formatjs/intl-datetimeformat/polyfill'
import '@formatjs/intl-datetimeformat/add-all-tz.js'

if ('__setDefaultTimeZone' in Intl.DateTimeFormat) {
  Intl.DateTimeFormat.__setDefaultTimeZone('America/Los_Angeles')
}

Tests#

This library is fully test262-compliant.