title: Year 0 gets corrupted
body: <pre><code>$datetime = new DateTime('0000-00-00 00:00:00');
  $date_string = $datetime-&gt;format('Y-m-d H:i:s');//-0001-11-30 00:00:00 
  </code></pre>
  
  <p>date gets turned from 0000-00-00 00:00:00 to -0001-11-30 00:00:00 
  this is obviously wrong, why does this happen, how to fix it?
  Should at least return false.</p>
  
  <p>info:
  PHP Version 5.2.13-0.dotdeb.1
  Linux 2.6.26-2-openvz-amd64 #1 SMP Thu Nov 25 05:14:47 UTC 2010 x86_64 </p>