DATE FUNCTION to Return a start time

FUNCTION get_oper_start_time(v_schedule_DATE DATE) RETURN DATE IS
BEGIN
RETURN to_DATE(to_char(v_schedule_DATE,'dd-mm-yyyy') || '08:00 AM', 'dd-mm-yyyy hh:mi AM');

EXCEPTION
WHEN OTHERS THEN
raise_application_error(-20000,'Exception (OTHERS) in get_oper_start_time '|| SQLERRM);
RETURN NULL;
END get_oper_start_time ;