title: Count number of days between two dates
body: <p>How do I count the number of days between these two dates?</p>
  
  <pre><code>start_date = Date.parse "2012-03-02 14:46:21 +0100"
  end_date =  Date.parse "2012-04-02 14:46:21 +0200"
  </code></pre>