title: Django ORM, group by day
body: <p>I am trying to group products by DAY, however date_created is a datetime field.</p>
  
  <pre><code>Product.objects.values('date_created') \
                 .annotate(available=Count('available_quantity'))
  </code></pre>
  
  <p>returns:</p>
  
  <pre><code>[
      {'date_created': datetime.datetime(2012, 4, 14, 13, 3, 6), 'available': 1},
      {'date_created': datetime.datetime(2012, 4, 14, 17, 12, 9), 'available': 1},
      ...
  ]
  </code></pre>
  
  <p>I want:</p>
  
  <pre><code>[
      {'date_created': datetime.datetime(2012, 4, 14), 'available': 2}, ...
  ]
  </code></pre>
  
  <p><strong>edit:</strong> database backend MYSQL</p>