title: Why I got Oracle error when I subtract one year from current date?
body: <p>I have this query on Oracle database 10g:</p>
  
  <pre><code>SELECT (CURRENT_DATE - INTERVAL '1' YEAR) FROM DUAL;
  </code></pre>
  
  <p>It was running correctly, but today I got this error:</p>
  
  <pre><code>ORA-01839: date not valid for month specified
  01839. 00000 -  "date not valid for month specified"
  *Cause:    
  *Action:
  </code></pre>
  
  <p>I know how I can avoid such error, but my question why it's thrown?</p>