Temporal.PlainYearMonth.prototype.since()

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 since() method of Temporal.PlainYearMonth instances returns a new Temporal.Duration object representing the duration from another year-month (in a form convertible by Temporal.PlainYearMonth.from()) to this year-month. The duration is positive if the other month is before this month, and negative if after.

This method does this - other. To do other - this, use the until() method.

Syntax

js
since(other)
since(other, options)

Parameters

other

A string, an object, or a Temporal.PlainYearMonth instance representing a year-month to subtract from this year-month. It is converted to a Temporal.PlainYearMonth object using the same algorithm as Temporal.PlainYearMonth.from(). It must have the same calendar as this.

options Optional

An object containing the options for Temporal.Duration.prototype.round(), which includes largestUnit, roundingIncrement, roundingMode, and smallestUnit. largestUnit and smallestUnit only accept the units: "years", "months", or their singular forms. For largestUnit, the default value "auto" means "years". For smallestUnit, the default value is "months". The current date is used as the relativeTo option.

Return value

A new Temporal.Duration object representing the duration since other to this year-month. The duration is positive if other is before this year-month, and negative if after.

Exceptions

RangeError

Thrown in one of the following cases:

  • other has a different calendar than this.
  • Any of the options is invalid.

Examples

Using since()

js
const lastUpdated = Temporal.PlainYearMonth.from("2022-01");
const now = Temporal.Now.plainDateISO().toPlainYearMonth();
const duration = now.since(lastUpdated);
console.log(`Last updated ${duration.toLocaleString("en-US")} ago`);
// Expected output: "Last updated [number] years, [number] months ago"

const duration2 = now.since(lastUpdated, { largestUnit: "months" });
console.log(`Last updated ${duration2.toLocaleString("en-US")} ago`);
// Expected output: "Last updated [number] months ago"

const duration3 = now.since(lastUpdated, { smallestUnit: "years" });
console.log(`Last updated ${duration3.toLocaleString("en-US")} ago`);
// Expected output: "Last updated [number] years ago"

Rounding the result

By default the fractional part of the smallestUnit is truncated. You can round it up using the roundingIncrement and roundingMode options.

js
const ym1 = Temporal.PlainYearMonth.from("2022-01");
const ym2 = Temporal.PlainYearMonth.from("2022-11");
const duration = ym2.since(ym1, {
  smallestUnit: "years",
  roundingMode: "ceil",
});
console.log(duration.toString()); // "P1Y"

Getting the result in days

By default, the resulting duration never contains days, because PlainYearMonth does not offer day-level precision. You can get the result in days by converting it to a Temporal.PlainDate first with an unambiguous day.

js
const ym1 = Temporal.PlainYearMonth.from("2022-01");
const ym2 = Temporal.PlainYearMonth.from("2022-11");
const duration = ym2.toPlainDate({ day: 1 }).since(ym1.toPlainDate({ day: 1 }));
console.log(duration.toString()); // "P304D"

Specifications

Specification
Temporal proposal
# sec-temporal.plainyearmonth.prototype.since

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
since
Experimental

Legend

Tip: you can click/tap on a cell for more information.

No support
No support
Experimental. Expect behavior to change in the future.
See implementation notes.
User must explicitly enable this feature.

See also