W3cubDocs

Intl.RelativeTimeFormat.prototype.format()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨September 2020⁩.

The format() method of Intl.RelativeTimeFormat instances formats a value and unit according to the locale and formatting options of this Intl.RelativeTimeFormat object.

Try it

const rtf = new Intl.RelativeTimeFormat("en", { style: "short" });

console.log(rtf.format(3, "quarter"));
// Expected output: "in 3 qtrs."

console.log(rtf.format(-1, "day"));
// Expected output: "1 day ago"

console.log(rtf.format(10, "seconds"));
// Expected output: "in 10 sec."

Syntax

format(value, unit)

Parameters

value: Numeric value to use in the internationalized relative time message.
unit: Unit to use in the relative time internationalized message. Possible values are: "year", "quarter", "month", "week", "day", "hour", "minute", "second". Plural forms are also permitted.

Return value

A string representing the given value and unit formatted according to the locale and formatting options of this Intl.RelativeTimeFormat object.

Note: Most of the time, the formatting returned by format() 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 format() to hardcoded constants.

Examples

Basic format usage

The following example shows how to create a relative time formatter using the English language.

// Create a relative time formatter in your locale
// with default values explicitly passed in.
const rtf = new Intl.RelativeTimeFormat("en", {
  localeMatcher: "best fit", // other values: "lookup"
  numeric: "always", // other values: "auto"
  style: "long", // other values: "short" or "narrow"
});

// Format relative time using negative value (-1).
rtf.format(-1, "day"); // "1 day ago"

// Format relative time using positive value (1).
rtf.format(1, "day"); // "in 1 day"

Using the auto option

If numeric:auto option is passed, it will produce the string yesterday, today, or tomorrow instead of 1 day ago, in 0 days, or in 1 day. This allows to not always have to use numeric values in the output.

// Create a relative time formatter in your locale
// with numeric: "auto" option value passed in.
const rtf = new Intl.RelativeTimeFormat("en", { numeric: "auto" });

// Format relative time using negative value (-1).
rtf.format(-1, "day"); // "yesterday"

rtf.format(0, "day"); // "today"

// Format relative time using positive day unit (1).
rtf.format(1, "day"); // "tomorrow"

Specifications

Specification
ECMAScript® 2026 Internationalization API Specification> # sec-Intl.RelativeTimeFormat.prototype.format>

Browser compatibility

	Desktop					Mobile							Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS	Bun	Deno	Node.js
`format`	71	79	65	58	14	71	65	50	14	10.0	71	14	1.0.0	1.8	12.0.0 Before version 13.0.0, only the locale data for `en-US` is available by default. See the `RelativeTimeFormat()` constructor for more details.