To know the actual date format, insert a record by using sysdate. That way you can find the actual date format. for example
insert into emp values(7936, 'Mac', 'clerk', 7782, sysdate, 1300, 300, 10);
now, select the inserted record.
select ename, hiredate from emp where ename='Mac';
the result is
ENAME HIREDATE
Mac 06-JAN-13
voila, now your actual date format is found.