An ISO week-numbering year (also called ISO year informally) has 52 or 53 full weeks. That is 364 or 371 days instead of the usual 365 or 366 days. The extra week is sometimes referred to as a leap week. [1]
A CalendarWeek implements a traversable seven day ISO week of a year.
A CalendarMonth implements a traversable ISO month of a year.
CalendarUnit has two enumeration implementations. These Enumerations localize weekday and month names. Implemented calendar unit instances can translate its name to various language by using IntlDateFormatter.
Weekday enumeration is used to specify an association between a weekday name and a weekday number.
Month enumeration is used to specify an association between month name and a month number.