The withCalendar() method of Temporal.ZonedDateTime instances returns a new Temporal.ZonedDateTime object representing this date-time interpreted in the new calendar system. Because all Temporal objects are designed to be immutable, this method essentially functions as the setter for the date-time's calendarId property.

The yearOfWeek accessor property of Temporal.PlainDate instances returns an integer representing the year to be paired with the weekOfYear of this date, or undefined if the calendar does not have a well-defined week system. It is calendar-dependent.

The valueOf() method of Temporal.PlainMonthDay instances throws a TypeError, which prevents Temporal.PlainMonthDay instances from being implicitly converted to primitives when used in arithmetic or comparison operations.

The Temporal.PlainMonthDay() constructor creates Temporal.PlainMonthDay objects.

The Temporal.PlainDate.compare() static method returns a number (-1, 0, or 1) indicating whether the first date comes before, is the same as, or comes after the second date. Equivalent to comparing the year, month, and day fields of the underlying ISO 8601 dates.

The add() method of Temporal.PlainDate instances returns a new Temporal.PlainDate object representing this date moved forward by a given duration (in a form convertible by Temporal.Duration.from()).

The calendarId accessor property of Temporal.PlainYearMonth instances returns a string representing the calendar used to interpret the internal ISO 8601 date.

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

The equals() method of Temporal.ZonedDateTime instances returns true if this date-time is equivalent in value to another date-time (in a form convertible by Temporal.ZonedDateTime.from()), and false otherwise. They are compared both by their instant values, time zones, and their calendars, so two date-times from different calendars or time zones may be considered equal by Temporal.ZonedDateTime.compare() but not by equals().

The toLocaleString() method of Temporal.PlainTime instances returns a string with a language-sensitive representation of this time. In implementations with Intl.DateTimeFormat API support, this method delegates to Intl.DateTimeFormat.