title: Ruby: how do I calculate a duration given 2 datetimes from a CSV file?
body: <p>I have a number of CSV files which contain start and finish times. I can use FasterCSV to parse the files, but I don't know the best way to get the duration in Ruby. Here are the values in my hash generated for each row of the CSV files.</p>
  
  <pre><code>start time: Mon Jul 20 18:25:17 -0400 2009
  end time: Mon Jul 20 18:49:43 -0400 2009
  </code></pre>