Calc Object Function dyinc() - increment date by number of days
 
   Format:
     dyinc(<jd>,<inc>)
       <jd> is the base numeric date
         In a Calc Object context, this value can be:
           . jdate() of a DATE field;
           . A DATETIME field;
           . A numeric variable derived from the jdate() of a DATE field;
           . A numeric variable derived from a DATETIME field;
         In a Calc Object context or a TQL context, this value can be:
           . jdate() of a DATE string literal or variable;
           . jdate64() of a DATETIME string literal or variable;;
           . A numeric variable;
           . Literal 0, which gives the current date and time;
       <inc> is the number of incremental days
         In a Calc Object context, this value can be:
           . A numeric field;
           . A string field that contains a numeric value;
         In a Calc Object context or a TQL context, this value can be:
           . A numeric literal or variable;
           . A string literal or variable that contains a numeric value;
 
   Result:
     The result of this function is a 64-bit floating number that represents
     a numeric DATE or DATETIME.
 
     The integer portion of this number is the number of days since 
     January 1, 1753.
 
     The fractional protion of this number represents the fractional 
     day contained in the time component of a DATETIME field.
 
     This value can be stored in a variable and used as the target of a
     DATE or DATETIME field in ddlWrite(), ddlChange() and Calc Object
     WRITE and REWRITE statements.
 
     It can be converted to a DATE string with the edate() function;
     it can be converted to a DATETIME string with the edate64() function.
 
   Comments:
     This function returns the specified <jd> incremented by <inc> days.