Dat = ww(Year,Week)
Dat = ww(Year,Month,Day)
Year [ numeric ] - Years.
Week [ numeric ] - Week of the year.
Month [ numeric ] - Calendar month.
Day [ numeric ] - Calendar day of the month Month.
Dat [ numeric ] - IRIS serial date number representing the weekly date.The IRIS weekly dates comply with the ISO 8601 definition:
every week starts on Monday and ends on Sunday;
the month or year to which the week belongs is determined by its Thurdsay.