Temporal.PlainDateTime.prototype.monthCode

Limited availability

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

The monthCode accessor property of Temporal.PlainDateTime instances returns a calendar-specific string representing the month of this date. It is calendar-dependent.

Usually it is M plus a two-digit month number. For leap months, it is the previous month's code followed by L (even if it's conceptually a derivative of the following month; for example, in the Hebrew calendar, Adar I has code M05L but Adar II has code M06). If the leap month is the first month of the year, the code is M00L.

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

For general information and more examples, see Temporal.PlainDate.prototype.monthCode.

Examples

Using monthCode

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

Specifications

Specification
Temporal
# sec-get-temporal.plaindatetime.prototype.monthcode

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
monthCode
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

Legend

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

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

See also