Temporal.ZonedDateTime.prototype.toLocaleString()

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The toLocaleString() method of Temporal.ZonedDateTime instances returns a string with a language-sensitive representation of this date-time. In implementations with Intl.DateTimeFormat API support, this method delegates to Intl.DateTimeFormat and passes this date-time converted to an Temporal.Instant (because Intl.DateTimeFormat cannot directly format a Temporal.ZonedDateTime).

Every time toLocaleString is called, it has to perform a search in a big database of localization strings, which is potentially inefficient. When the method is called many times with the same arguments, it is better to create a Intl.DateTimeFormat object and use its format() method, because a DateTimeFormat object remembers the arguments passed to it and may decide to cache a slice of the database, so future format calls can search for localization strings within a more constrained context. However, currently Intl.DateTimeFormat does not support formatting Temporal.ZonedDateTime objects, so you must convert them to Temporal.Instant objects first before passing them to format().

Syntax

toLocaleString()
toLocaleString(locales)
toLocaleString(locales, options)

Parameters

The locales and options parameters customize the behavior of the function and let applications specify the language whose formatting conventions should be used.

In implementations that support the Intl.DateTimeFormat API, these parameters correspond exactly to the Intl.DateTimeFormat() constructor's parameters. Implementations without Intl.DateTimeFormat support return the exact same string as toString(), ignoring both parameters.

locales Optional

A string with a BCP 47 language tag, or an array of such strings. Corresponds to the locales parameter of the Intl.DateTimeFormat() constructor.

options Optional

An object adjusting the output format. Corresponds to the options parameter of the Intl.DateTimeFormat() constructor. If this date-time's calendar is not "iso8601", the calendar option must be provided with the same value; otherwise, if this date-time's calendar is "iso8601", the calendar option can be any value. The timeZone option must not be provided, as it is automatically set to be the date-time's timeZoneId. Regarding the date-time component options and the style shortcuts (dateStyle and timeStyle), the options should follow one of these forms:

Provide none of them: year, month, day, hour, minute, and second will default to "numeric".
Provide at least one of dateStyle or timeStyle: the date-time components will be set according to the specified style and the locale.
Provide some date-time component options. Only the specified date-time components will be included in the output.

See the Intl.DateTimeFormat() constructor for details on these parameters and how to use them.

Return value

A string representing the given date-time according to language-specific conventions.

In implementations with Intl.DateTimeFormat, this is equivalent to new Intl.DateTimeFormat(locales, options).format(dateTime.toInstant()), where options has been normalized as described above.

Note: Most of the time, the formatting returned by toLocaleString() is consistent. However, the output may vary between implementations, even within the same locale — output variations are by design and allowed by the specification. It may also not be what you expect. For example, the string may use non-breaking spaces or be surrounded by bidirectional control characters. You should not compare the results of toLocaleString() to hardcoded constants.

Exceptions

RangeError: Thrown if any of the options is invalid.
TypeError: Thrown if any of the options is not of the expected type.

Examples

Using toLocaleString()

Basic use of this method without specifying a locale returns a formatted string in the default locale and with default options.

const zdt = Temporal.ZonedDateTime.from(
  "2021-08-01T12:34:56-04:00[America/New_York]",
);

console.log(zdt.toLocaleString()); // 8/1/2021, 12:34:56 PM EDT (assuming en-US locale)

If the date's calendar doesn't match the locale's default calendar, and the date's calendar is not iso8601, an explicit calendar option must be provided with the same value.

const zdt = Temporal.ZonedDateTime.from(
  "2021-08-01T12:34:56+09:00[Asia/Tokyo][u-ca=japanese]",
);
// The ja-JP locale uses the Gregorian calendar by default
zdt.toLocaleString("ja-JP", { calendar: "japanese" }); // R3/8/1 12:34:56 JST

Using toLocaleString() with options

You can customize which parts of the date are included in the output by providing the options parameter.

const zdt = Temporal.ZonedDateTime.from(
  "2021-08-01T12:34:56+09:00[Asia/Tokyo][u-ca=japanese]",
);
zdt.toLocaleString("ja-JP", {
  calendar: "japanese",
  dateStyle: "full",
  timeStyle: "full",
}); // 令和3年8月1日日曜日 12時34分56秒 日本標準時
zdt.toLocaleString("ja-JP", {
  calendar: "japanese",
  year: "numeric",
  month: "long",
  hour: "numeric",
  timeZoneName: "shortGeneric",
}); // 令和3年8月 12時 JST
zdt.toLocaleString("ja-JP", {
  calendar: "japanese",
  year: "numeric",
  hour: "numeric",
  minute: "numeric",
}); // 令和3年 12:34

Specifications

Specification
Temporal proposal # sec-temporal.zoneddatetime.prototype.tolocalestring

Browser compatibility

	Desktop					Mobile						Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	Deno	Node.js
`toLocaleString`	No	No	No	No	No	No	No	No	No	No	No	1.40	No