A Simple Math Formula to Get Special Dates

CREATE OR REPLACE PROCEDURE GETREQUIREDDATE ( 
          inputDate int, basedate date, res OUT date) 
AS 
  add_day      int;
  minus_day    int;
  diff_day     int;
  days         int;
  
BEGIN
    days       :=  to_NCHAR( to_date(baseDate), 'D');    
    add_day    := mod((inputDate - days + 7),7);
    minus_day  := mod((inputDate - days - 7), 7);
    diff_day   := (1- floor(abs(add_day)/3.5)) * add_day + (1-floor(abs(minus_day)/3.5)) * minus_day;
    res        := basedate + diff_day;
    
EXCEPTION
 WHEN OTHERS THEN
       raise_application_error(-20001,'An error was encountered - '||SQLCODE||' -ERROR- '||SQLERRM);

END GETREQUIREDDATE;