SYNTAX            : <Date value> ;D

RESULTING ARGUMENT: Day of the week

FUNCTION          : Determine day of the week for a given date.

ARGUMENT          : Date value, format YYYMMDD.

NOTE              : Days are numbered as follows:
                    Monday     = 1
                    Tuesday    = 2
                    Wednesday  = 3
                    Thursday   = 4
                    Friday     = 5
                    Saturday   = 6
                    Monday     = 7
                    Other numbers cannot be returned.

MATRIX