# Contributors by commit history https://github.com/mdn/content/commits/main/files/en-us/web/javascript/reference/global_objects/temporal/plainmonthday/toplaindate/index.md 174

The timeZoneId accessor property of Temporal.ZonedDateTime instances returns a string representing the time zone identifier used to interpret the internal instant. The string is either a named identifier in the preferred case (such as "America/New_York"), or an offset in the form "±hh:mm". If the time zone has aliases, the timeZoneId is the identifier used to create the ZonedDateTime, without canonicalization to the primary identifier.

The toPlainTime() method of Temporal.PlainDateTime instances returns a new Temporal.PlainTime object representing the time part (hour, minute, second, and subsecond components) of this date-time.

The toPlainDateTime() method of Temporal.PlainDate instances returns a new Temporal.PlainDateTime object representing this date and a supplied time in the same calendar system.

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

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().

# Contributors by commit history https://github.com/mdn/content/commits/main/files/en-us/web/javascript/reference/global_objects/temporal/index.md 148

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

The dayOfYear accessor property of Temporal.PlainDate instances returns a positive integer representing the 1-based day index in the year of this date. The first day of this year is 1, and the last day is the daysInYear. It is calendar-dependent.