title: Algorithm for clustering pictures based on date taken
body: <p>Anyone know of an algorithm that will group pictures into events based on the date the picture was taken.  Obviously I can group by the date, but I'd like something a little more sophisticated that would(might) be able to group pictures spanning multiple days based on the frequency over a certain timespan. Consider the following groupings:</p>
  
  <ul>
  <li>1/2/2009 15 photos </li>
  <li>1/3/2009 20 photos</li>
  <li>1/4/2009 13 photos</li>
  <li>1/5/2009 19 photos</li>
  <li>1/15/2009 5 photos</li>
  </ul>
  
  <p>Potentially these would be grouped into two groups:</p>
  
  <ol>
  <li>1/2/2009 -> 1/5/2009 </li>
  <li>1/15/2009</li>
  </ol>
  
  <p>Obviously there will be some tolerance(s) that need to be established.  </p>
  
  <p>Is there any well established way of doing this, other then inventing my own top/down approach?</p>