Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The calendarId accessor property of Temporal.PlainMonthDay instances returns a string representing the calendar used to interpret the internal ISO 8601 date.
For a list of commonly supported values, see Intl.Locale.prototype.getCalendars().
The set accessor of calendarId is undefined. You cannot change this property directly. There's no obvious way to create a new Temporal.PlainMonthDay object with a different calendar that represents the same month-day, so you need to convert it to a Temporal.PlainDate object first using toPlainDate(), change the calendar, and then convert it back.