function WWFormula return Number is
A NUMBER;
begin
 select trunc((last_day(dt) - trunc(dt,'iw') + 1) / 7) * 6 +
          least(mod(last_day(dt) - trunc(dt,'iw') + 1,7),6) -
least(dt - trunc(dt,'iw'),6) 
   INTO A from  (
           select  add_months(to_date('01-MAR-2017','DD/MM/YYYY'),level - 1) dt
             from  dual
             connect by level <= 12);
         return(a);
end;

no : to_date('01-MAR-2017', 'DD/MM/YYYY')
yes: to_date('01-mar-2017', 'dd-mon-yyyy')

no : to_date('01-mar-2017', 'dd-mon-yyyy')
yes: to_date('01.03.2017', 'dd.mm.yyyy')