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
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
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