title: Django GROUP BY strftime date format
body: <p>I would like to do a SUM on rows in a database and group by date.</p>
  
  <p>I am trying to run this SQL query using Django aggregates and annotations:</p>
  
  <pre><code>select strftime('%m/%d/%Y', time_stamp) as the_date, sum(numbers_data)
      from my_model
      group by the_date;
  </code></pre>
  
  <p>I tried the following:</p>
  
  <pre><code>data = My_Model.objects.values("strftime('%m/%d/%Y',
             time_stamp)").annotate(Sum("numbers_data")).order_by()
  </code></pre>
  
  <p>but it seems like you can only use column names in the values() function; it doesn't like the use of strftime().</p>
  
  <p>How should I go about this?</p>