Date
class Date
date and datetime class - Tadayoshi Funaba 1998-2011
'date' provides two classes: Date and DateTime.
Terms and Definitions
Some terms and definitions are based on ISO 8601 and JIS X 0301.
Calendar Date
The calendar date is a particular day of a calendar year, identified by its ordinal number within a calendar month within that year.
In those classes, this is so-called “civil”.