Temporal.PlainDate.prototype.month

Limited availability

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

See full compatibility

The month accessor property of Temporal.PlainDate instances returns a positive integer representing the 1-based month index in the year of this date. The first month of this year is 1, and the last month is the monthsInYear. It is calendar-dependent.

Note that unlike Date.prototype.getMonth(), the index is 1-based. If the calendar has leap months, then the month with the same monthCode may have different month indexes for different years.

Note: Do not use this property to identify the actual month, including its name. Use monthCode for that purpose. Use month only for identifying months within the context of a year, or to figure out their order.

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

Examples

Using month

const date = Temporal.PlainDate.from("2021-07-01"); // ISO 8601 calendar
console.log(date.monthCode); // "M07"
console.log(date.month); // 7

const date2 = Temporal.PlainDate.from("2021-05-01[u-ca=chinese]");
console.log(date2.monthCode); // "M03"
console.log(date2.month); // 3; it is March 20 in the Chinese calendar

const date3 = Temporal.PlainDate.from("2023-05-01[u-ca=chinese]");
console.log(date3.monthCode); // "M03"
console.log(date3.month); // 4, although it is also March (M03)!

const date4 = Temporal.PlainDate.from("2023-04-01[u-ca=chinese]");
console.log(date4.monthCode); // "M02L"
console.log(date4.month); // 3, this month is a leap month, i.e. a duplicate February

Looping through all months in a year

const year = Temporal.PlainDate.from("2021-07-14"); // An arbitrary date in the year
for (
  let month = year.with({ month: 1 });
  month.year === year.year;
  month = month.add({ months: 1 })
) {
  console.log(month.month);
}

Alternatively, this is also a safe way (unlike the day example):

for (let month = 1; month <= year.monthsInYear; month++) {
  const monthDate = year.with({ month });
}

Changing month

const date = Temporal.PlainDate.from("2021-07-01");
const newDate = date.with({ month: 2 });
console.log(newDate.toString()); // 2021-02-01

You can also use add() or subtract() to move a certain number of months from the current date.

const date = Temporal.PlainDate.from("2021-07-01");
const newDate = date.add({ months: 3 });
console.log(newDate.toString()); // 2021-10-01

By default, with() constrains the day to the range of valid values. Both of the following will set the month to the last month of the year:

const date = Temporal.PlainDate.from("2021-07-01");
const lastMonth = date.with({ month: date.monthsInYear }); // 2021-12-01
const lastMonth2 = date.with({ month: Number.MAX_VALUE }); // 2021-12-01

Specifications

Specification
Temporal # sec-get-temporal.plaindate.prototype.month

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
`month`	Chrome – Full support Chrome 144 (Release date: 2026-01-13) footnote Full support	Edge – Full support Edge 144 (Release date: 2026-01-21) footnote Full support	Firefox – Full support Firefox 139 (Release date: 2025-05-27) footnote Full support	Opera – Full support Opera 128 (Release date: 2026-02-26) footnote Full support	Safari – No support Safari footnote footnote See bug 223166	Chrome Android – Full support Chrome Android 144 (Release date: 2026-01-13) footnote Full support	Firefox for Android – Full support Firefox for Android 139 (Release date: 2025-05-27) footnote Full support	Opera Android – Full support Opera Android 95 (Release date: 2026-02-11) footnote Full support	Safari on iOS – No support Safari on iOS footnote footnote See bug 223166	Samsung Internet – No support Samsung Internet footnote No support	WebView Android – Full support WebView Android 144 (Release date: 2026-01-13) footnote Full support	WebView on iOS – No support WebView on iOS footnote footnote See bug 223166	Bun – No support Bun footnote No support	Deno – Full support Deno 2.7 (Release date: 2026-02-25) footnote Full support	Node.js – No support Node.js footnote No support

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Full support: Full support
No support: No support
: See implementation notes.