title: Plotting Number of Events that Occur in an Interval Histogram
body: <p>In Excel, I have two fields per row, a start date/time and an end date/time.  I am looking to plot a histogram that shows how many of the rows' intervals contain the time on the x axis.</p>
  
  <p>For example, some start and end times could be: [1,3], [3,4], [7,9], and [7,8]</p>
  
  <p>And I want an output similar to:</p>
  
  <pre><code>    x       x x
  x x x x     x x x
  1.2.3.4.5.6.7.8.9
  </code></pre>
  
  <p>How can this be done?</p>