Quick Date Question

Question

I'm working on a system with a lot of date validations. The validations that I built work fine as long as someone uses the correct format. The code that I'm using is:
DECLARE
DATE_CHECK DATE;
DOB_CHECK DATE;
BEGIN
BEGIN
DOB_CHECK := to_date(:P32_DOB, 'MM/DD/YYYY');
DATE_CHECK := to_date(:P32_DI_UR_DT, 'MM/DD/YYYY');
IF DOB_CHECK > DATE_CHECK
THEN
RETURN 'Urine condition onset date cannot occur before birth date.';
END IF;
EXCEPTION
WHEN OTHERS THEN
RETURN 'Urine condition onset date not a valid date.';
END;
END;
Like I said. This works correctly, as long as someone uses the four-digit year. If they only use a two-digit year (08/04/09) it keeps throwing the error that it is occurring before the birth date.
I have used JavaScript in other programs so that I could automatically format any date that is put in to the format that I want. The problem is that I can't use that functionality in this case because it will create an infinite loop.
So, my question is this: How can I isolate the year of the date in PL/SQL so that I can add either 19 or 20 to the beginning of the year so that it conforms to the format I'm using?
Thanks in advance.
Josh

Answer 1

I would strongly advise a javascript validation to check the four digit year was supplied.
However the modified code below adds 19 or 20 to the input year.
But what if your software will beyond 2100?
Or what if you have a Dracula patient born before 1900?
DECLARE
   date_check   DATE;
   dob_check    DATE;
   FUNCTION add_century(p_sdate IN VARCHAR2)
   RETURN VARCHAR2
   IS
   BEGIN
      RETURN CASE WHEN LENGTH(p_sdate )<10
                    THEN CASE WHEN TO_NUMBER(SUBSTR(p_sdate ,-2)) <= TO_NUMBER(TO_CHAR(SYSDATE,'YY'))
                              THEN  SUBSTR(p_sdate ,1,6)||'20'||SUBSTR(p_sdate ,-2)
                              ELSE  SUBSTR(p_sdate ,1,6)||'19'||SUBSTR(p_sdate ,-2)
                          END   
                    ELSE p_sdate
                END;
   END;
BEGIN
   BEGIN
      dob_check := TO_DATE (add_century(:p32_dob), 'MM/DD/YYYY');
      date_check := TO_DATE (add_century(:p32_di_ur_dt), 'MM/DD/YYYY');
      IF dob_check > date_check
      THEN
        RETURN 'Urine condition onset date cannot occur before birth date.';
      END IF;
   EXCEPTION
      WHEN OTHERS
      THEN
          RETURN 'Urine condition onset date not a valid date.';
   END;
END;