new PlainMonthDay()
Description
The new Temporal.PlainMonthDay() constructor creates a new
Temporal.PlainMonthDay object.
Syntax
new Temporal.PlainMonthDay(month, day, calendar, referenceYear)
Parameters
| Parameters | Description |
| month | A number representing a month in the calendar. |
| day | A number representing a day in the calendar. |
| calendar | Default "iso8601". A string representing the calendar. |
| referenceYear | Default 1972. A number representing the year the ISO calendar system. |
Warning
Avoid using calendar and referenceYear, because equals() will consider two equivalent dates to be different if they have different reference days.
To create a PlainMonthDay object with a non-ISO calendar, use the Temporal.PlainMonthDay.from() method.
Return Value
| Type | Description |
| Object | A new Temporal.PlainMonthDay object. |
Browser Support
Temporal is a major update to the JavaScript standard (TC39).
It is currently supported in Chrome, Edge, Firefox, and Opera Safari has not shipped it yet.
| Chrome 144 |
Edge 144 |
Firefox 139 |
Safari |
Opera 128 |
| Jan 2026 | Jan 2026 | May 2025 | 🚫 | Feb 2026 |
The Safari implementation can be tested in Safari Technology Preview by enabling the --use-temporal runtime flag.
Polyfill
Until Safari supports Temporal natively, you can use the official polyfill:
<script
src="https://cdn.jsdelivr.net/npm/@js-temporal/polyfill@0.5.1/dist/index.umd.js">
</script>