title: datejs TimeSpan and TimePeriod problems
body: <p>I'm losing the plot with this one.  I've added date.js and time.js to my project.</p>
  
  <p>I then having the following test code:</p>
  
  <pre><code>  1  var a = Date.today();
    2  var b = Date.today().next().friday();
    3  var ts = new TimeSpan(b - a);
    4  alert(ts.getDays());
  </code></pre>
  
  <p>I think everything is correct, yet i receive the following error:</p>
  
  <blockquote>
    <p>Object doesn't support this property or method at line 4!</p>
  </blockquote>