title: How to group by a date column by month
body: <p>I have a table with a date column where date is stored in this format:</p>
  
  <pre><code>2012-08-01 16:39:17.601455+0530
  </code></pre>
  
  <p>How do I <code>group</code> or <code>group_and_count</code> on this column by <code>month</code>?</p>