title: Why this operation with date (number of days between 2 dates) return this value?
body: <p>According to <a href="https://stackoverflow.com/questions/2627473/how-to-calculate-the-number-of-days-between-two-dates-using-javascript">this</a> question, I wrote "my code" (without Math.abs, I don't need it) :</p>
  
  <pre><code>var oneDay = 24 * 60 * 60 * 1000; // hours*minutes*seconds*milliseconds
  var firstDate = new Date("2011", "09", "28"); // 28 september 2011
  var secondDate = new Date("2011", "09", "30"); // 30 september 2011
  
  var notti = ((secondDate.getTime() - firstDate.getTime()) / (oneDay));
  if (notti &lt; 1)
      notti = 1;
  else
      notti = Math.round(notti);
  
  alert(notti);
  </code></pre>
  
  <p>and it print 2 (correct). </p>
  
  <p>Now, If I do this :</p>
  
  <pre><code>var oneDay = 24 * 60 * 60 * 1000; // hours*minutes*seconds*milliseconds
  var firstDate = new Date("2011", "09", "28"); // 28 september 2011
  var secondDate = new Date("2011", "10", "01"); // 01 october 2011
  
  var notti = ((secondDate.getTime() - firstDate.getTime()) / (oneDay));
  if (notti &lt; 1)
      notti = 1;
  else
      notti = Math.round(notti);
  
  alert(notti);
  </code></pre>
  
  <p>it print 4. Why 4? It should be 3...
  Do you know about this problem?</p>