FT_WOY()
 Find number of week within year

 Syntax

      FT_WOY( <dDate> ) -> <nResult>

 Arguments

     <dDate> is a date in the form "mm/dd/yy" or "mm/dd/yyyy"

 Returns

     Return numeric position of week within the year or NIL if
     parameter does not conform.

 Description

     Considers a full week as starting on Sunday, ending on Saturday.
     First week of year (week 1) may start on any day, and thus
       contain any number of days.
     Final week of year (week 53) may contain any number of days.
     Handles dates with CENTURY ON|OFF, to allow for 21st century.
     Date validation must be external to this function.

 Examples

     These code fragments find the week number, given a date.

     // literal character date
     dDate  := CTOD("01/01/91")
     nWkNum := FT_WOY(dDate)              // result:  1

     // presume DOS date to be 01/06/91
     nWkNum := FT_WOY(DATE())             // result:  2

     // date input
     cDate  := SPACE(8)
     @ 4,10 get cDate PICT "##/##/##"     // input 07/04/91
     READ
     nWkNum := FT_WOY(CTOD(cDate))        // result: 27

     // last day of year
     nWkNum := FT_WOY(CTOD("12/31/91"))    // result: 53

     For a demonstration of this function, compile and link the
     program WOY.PRG in the Nanforum Toolkit source code.

 Source: WOY.PRG

 Author: Forest Belt, Computer Diagnostic Services, Inc.