title: Django filter by week
body: <p>Is there a way to easily filter Date objects by week? Basically I want to do something like </p>
  
  <p><code>items= RelevantObject.objects.filter(date__week=32)</code></p>
  
  <p>I've found that it's possible to do this for year and month, but it doesn't seem like the capability for week is built in. Is there a "right" way to do this? It seems like it shouldn't be too difficult. </p>
  
  <p>Thanks </p>