The calendarId accessor property of Temporal.PlainDate instances returns a string representing the calendar used to interpret the internal ISO 8601 date.
See Intl.supportedValuesOf() for a list of commonly supported calendar types.
The set accessor of calendarId is undefined. You cannot change this property directly. Use the withCalendar() method to create a new Temporal.PlainDate object with the desired new value.
const date = Temporal.PlainDate.from("2021-07-01");
console.log(date.calendarId); // "iso8601"; default
const date2 = Temporal.PlainDate.from("2021-07-01[u-ca=chinese]");
console.log(date2.calendarId); // "chinese"
const date3 = date2.withCalendar("hebrew");
console.log(date3.calendarId); // "hebrew"