Provides localized date/time format patterns for styles full, long, medium and short, using Intl.DateTimeFormat. For example:

const formatter = new Intl.DateTimeFormat('cs', { dateStyle: 'short'})
const pattern = getDateTimeFormatPattern(formatter) // d.M.yy

• ES, CJS and UMD module exports.
• TypeScript type declarations (typings).
• No other dependencies.
• Tiny code base - 2.73 kB minified, 1.31 B gzipped, 1.16 B brotlied.
• Resolves four date/time-formatting pattern styles (lengths) - full, long, medium, short.

This library needs a working implementation of Intl.DateTimeFormat.If you are interested in a library, which does not need Intl.DateTimeFormat and uses CLDR data to be compliant with Unicode LDML too, have look at datetime-locale-patterns.

Related projects:

• date-and-time-formatter - formats a date/time value to a localised string using a pattern consisting of Unicode LDML tokens.
• datetime-placeholder - simplifies a date/time-formatting pattern using Unicode LDML tokens to a pattern usable in date/time pickers.
• datetime-locale-patterns - provides localized date/time format patterns for styles full, long, medium and short using Unicode CLDR, compliant with Unicode LDML.
• intl-datetimeformat-pattern - creates a valid Intl.DateTimeFormat options object from a Unicode CLDR skeleton or token pattern.

When do you need to know the date/time format pattern? When is just formatting a date or time values to a string not enough?

1. Date/time pickers. You format with Intl.DateTimeFormat. Intl.DateTimeFormat or luxon format using a localized pattern decided by a specified locale. No need to provide the format explicitly. But what if you need to display the format pattern, which is used for the formatting? For example, in a date picker field as a value placeholder.
2. Raw date/time formatting. You do not format with Intl.DateTimeFormat. Libraries like date-and-time, date-fns and others format using patterns provided by the developer. But how to get a localized pattern for a particular language and country?

There is no built-in API in browsers or Node.js for getting localized date/time-formatting patterns.

1. Date/time pickers. Get a pattern to see in an abstract way how a concrete date will be formatted:

import { getDateTimeFormatPattern } from 'intl-datetimeformat-options'

const date = new Date(1, 1, 3, 4, 5, 6)
const options = { dateStyle: 'short', timeStyle: 'short' }

const formatter = new Intl.DateTimeFormat('en', options)
const text = formatter.format(date)
console.log(text) // prints '2/3/01, 4:05 AM'

const pattern = getDateTimeFormatPattern('en', options)
console.log(pattern) // prints 'M/d/yy, h:mm a'

2. Raw date/time formatting. Get a pattern to format a concrete date with:

import { getDateTimeFormatPattern } from 'intl-datetimeformat-options'
import formatter from 'date-and-time'

const date = new Date(1, 1, 3, 4, 5, 6)

const pattern = getDateTimeFormatPattern('en', 'short', 'short')
console.log(pattern) // prints 'M/d/yy, h:mm a'

const text = formatter.format(date, pattern)
console.log(text) // prints '2/3/01, 4:05 AM'

This module can be installed in your project using NPM, PNPM or Yarn. Make sure, that you use Node.js version 16.14 or newer.

$ npm i intl-datetimeformat-options
$ pnpm i intl-datetimeformat-options
$ yarn add intl-datetimeformat-options

Functions are exposed as named exports from ES and CJS modules, for example:

import { getDateTimeFormatPattern } from 'intl-datetimeformat-options'

const { getDateTimeFormatPattern } = require('intl-datetimeformat-options')

A UMD module can be loaded to the browser either directly:

<script src="https://unpkg.com/[email protected]/lib/index.min.js"></script>
<script>
  const { getDateTimeFormatPattern } = window.intlDateTimeFormatOptions
</script>

Or using an AMD module loader:

<script>
  require([
    'https://unpkg.com/[email protected]/lib/index.min.js'
  ], ({ getDateTimeFormatPattern }) => {
    ...
  })
</script>

This library works well with Intl.DateTimeFormat by using concepts from Unicode CLDR (Common Locale Data Repository):

• It expects Unicode locales (2-letter and 3-letter languages and countries from ISO 639 and ISO 3166, formatted according to extended BCP 47), which Intl locales is based on.
• It supports Unicode calendar formats - date, time, dateTime.
• It expects Unicode pattern styles (lengths) - full, long, medium, short, as dateStyle and timeStyle properties of Intl.DateTimeFomat options do.
• It supplies date/time-formatting patterns using date fields from Unicode LDML (Locale Data Markup Language) as tokens.

Returns a pattern to format a date+time value for the specified locale with the specified style.

The locale argument can be either a locale or an instance of Intl.DateTimeFomat. The second argument won't be needed in the latter case.

The dateStyle argument can be either a string (full, long, medium, short) or an object with dateStyle and timeStyle properties from Intl.DateTimeFomat options. If it is a string, the timeStyle argument will be required (as a string).

import { getDateTimeFormatPattern } from 'intl-datetimeformat-options'

const pattern = getDateTimeFormatPattern('en', 'short', 'short')
console.log(pattern) // prints 'M/d/yy, h:mm a'

The patterns are guessed by formatting a specific date (1901-02-03 04:05:06), parsing the formatted output and detecting numeric formats, names of days and months and other tokens from Unicode LDML. This needs a reliable implementation of Intl.DateTimeFormat.

• If the date/time formatting provided by the underlying OS API is used in the implementation of Intl.DateTimeFormat, the actual pattern may differ from the multi-platform Unicode CLDR.
• If ICU (International Components for Unicode) library, which is supposed to be in sync with Unicode CLDR, is used by a browser or Node.js, the version of that ICU may differ from the latest version of Unicode CLDR and from the implementation of Intl.DateTimeFormat. This can be seen in long and full styles of the en locale, which include a different "glue pattern" for joining data and time patterns. ICU includes " at ", while Unicode CLDR includes ",".

Patterns returned by this library should match the behaviour of Intl.DateTimeFormat well. Patterns from Unicode CLDR may differ.

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using Grunt.

Copyright (c) 2023 Ferdinand Prantl

Licensed under the MIT license.