CREATE OR REPLACE FUNCTION WB_IS_DATE_MY ("P_VAR" IN VARCHAR2,  "P_FORMAT" IN VARCHAR2) RETURN NUMBER  IS 
p_date DATE;
BEGIN
if (p_format is null) then  p_date := TO_DATE(p_var);
else
p_date := TO_DATE(p_var, p_format);
end if;
IF (p_date is null) then return 0;
else return 1;
end if;
EXCEPTION
WHEN OTHERS THEN
RETURN 0;
END;
/