title: How to represent a date time for B.C. within python
body: <p>I am creating a application about the history. But I am getting stuck when I need to create a field with django <code>DateTimeField</code> to represent the date time for B.C.(aka Before Christ).</p>
  
  <p>eg. Roman Empire is from 27 B.C. to 395 AD. How can I represent the <code>from</code> and <code>to</code> date with python <code>datetime</code> or django <code>DateTimeField</code>? </p>
  
  <p>I need some further date calculation on these fields, so an <code>integer</code> is not quite well for this, any idea?</p>