Find the difference between the given date and 31-DEC-2002.

Then find the entry with the smallest difference.

This might help:

SQL> select to_date('31-DEC-2002', 'DD-MON-YY') - SYSDATE
2 from dual;

TO_DATE('31-DEC-2002','DD-MON-YY')-SYSDATE
------------------------------------------
18.4627546