is date() function for Oracle

[jmodic]

Isn't this one more simple:

create or replace function check_dateformat(p_date_input varchar2) 
return boolean is
  lv_date_return DATE ;
  return_value BOOLEAN := TRUE;
BEGIN
  BEGIN
    lv_date_return := TO_DATE (p_date_input, 'DD-MM-YYYY'); 
    IF lv_date_return NOT BETWEEN TO_DATE ('01-01-1900', 'DD-MM-YYYY') AND TO_DATE ('01-01-1900', 'DD-MM-YYYY') THEN
      return_value := FALSE;
    END IF; 
  EXCEPTION
    WHEN OTHERS THEN return_value := FALSE;
  END;
RETURN return_value;
END;

Why even bother with checking months and day of months, with leap years and so on - it is all implicitly checked in a TO_DATE function.

I only left the year range checking if you realy need to check this, otherwise you should simply throw that part out.