The "Date" data type provides support for expressing individual points in time. The precision with which the time point may be specified varies from year-level to the level of a second. Dates are given and displayed in the ISO-standard format, i.e. YYYY-MM-DD hh:mm:ss (YYYY = year in the range 0000-9999, MM = arithmetic month of the Gregorian calendar in the range 1-12, DD = day within the month in the range 1-31, hh = hour in the range 0-23, mm = minute in the range 0-59 and ss = second in the range 0-59). The following examples illustrate acceptable values for a date slot:
- 2006
- 2006-03
- 2006-03-25
- 2006-03-25 10
- 2006-03-25 10:58
- 2006-03-25 10:58:43
The precision used to denote the time quantity will be termed as granularity in this document. Note that the year is mandatory. Two more values are acceptable as dates, more specifically the strings unknown and now. The unknown value can be used to signify that the date is not known, while the now value should be interpreted as always being equal to the current "wall clock" indication.