Calculates the week number for a date you enter.

       (The week number is an integer from 1 to 52. A week number is
       assigned sequentially to each week, beginning with the first
       week of the year. The first week of January is week number 1, the
       second week of January is week number 2, and so on.)

1  –  Input

       A date.

2  –  Output

       An unsigned integer from 1 to 52.

3  –  Example

       DTR> DECLARE CAL USAGE DATE EDIT_STRING X(23).
       DTR> CAL = "NOW"; PRINT CAL

                 CAL

        1-Feb-1983 08:51:11.55

       DTR> PRINT FN$WEEK (CAL)

         FN$WEEK

                5

       DTR>