title: ADD_MONTHS function does not return the correct date in Oracle
body: <p>See the results of below queries:</p>
  
  <pre><code>&gt;&gt; SELECT ADD_MONTHS(TO_DATE('30-MAR-11','DD-MON-RR'),-4) FROM DUAL;
  30-NOV-10
  
  
  &gt;&gt; SELECT ADD_MONTHS(TO_DATE('30-NOV-10','DD-MON-RR'),4) FROM DUAL;
  31-MAR-11
  </code></pre>
  
  <p>How can I get '30-MAR-11' when adding 4 months to some date?</p>
  
  <p>Please help.</p>