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 and is expected to reach full availability across browsers before the summer of 2026.
| 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 support Temporal natively, you can use the official polyfill:
<script
src="https://cdn.jsdelivr.net/npm/@js-temporal/polyfill/dist/index.umd.js">
</script>