Date
A date is a three-part value (year, month, and day) designating a point in time using the Gregorian calendar, which is assumed to have been in effect from the year 1 A.D.
The range of the year part is 0001 to 9999. The range of the month part is 1 to 12. The range of the day part is 1 to 28, 29, 30, or 31, depending on the month and year.1
The internal representation of a date is a string of 4 bytes. Each byte consists of two packed decimal digits. The first 2 bytes represent the year, the third byte the month, and the last byte the day.
A character-string representation must have an actual length that is not greater than 255 bytes.
1 Historical dates do not always
follow the Gregorian calendar. Dates between 1582-10-04 and 1582-10-15
are accepted as valid dates although they never existed in the Gregorian
calendar.