Temporal.Duration.prototype.months

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 months accessor property of Temporal.Duration instances returns an integer representing the number of months in the duration.

Unless the duration is balanced, you cannot assume the range of this value, but you can know its sign by checking the duration's sign property. If it is balanced to a unit above months, the months absolute value's range depends on the calendar (how many months are in a year).

The set accessor of months is undefined. You cannot change this property directly. Use the with() method to create a new Temporal.Duration object with the desired new value.

Examples

Using months

js
const d1 = Temporal.Duration.from({ years: 1, months: 1 });
const d2 = Temporal.Duration.from({ years: -1, months: -1 });
const d3 = Temporal.Duration.from({ years: 1 });
const d4 = Temporal.Duration.from({ months: 12 });

console.log(d1.months); // 1
console.log(d2.months); // -1
console.log(d3.months); // 0
console.log(d4.months); // 12

// Balance d4
const d4Balanced = d4.round({
  largestUnit: "years",
  relativeTo: Temporal.PlainDate.from("2021-01-01"), // ISO 8601 calendar
});
console.log(d4Balanced.months); // 0
console.log(d4Balanced.years); // 1

Specifications

Specification
Temporal proposal
# sec-get-temporal.duration.prototype.months

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
months
Experimental

Legend

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

In development. Supported in a pre-release version.
In development. Supported in a pre-release version.
No support
No support
Experimental. Expect behavior to change in the future.
See implementation notes.
User must explicitly enable this feature.

See also