title: How to convert two dates difference into hours only?
body: <p>I'd like to display the time difference between two dates in hours and minutes <code>HH:mm</code>. If the difference is more than 24 hours, the days/years difference should also only be displayed as total hours.</p>
  
  <p>I have the following, but it might be incorrect for leap years for example. So I feel it is not the right way. I also have to take GMT time differences into account. How could I improve that:</p>
  
  <pre><code>Calendar start; //eg 18.11.2013+05:00
  Calendar end; //eg 20.11.2013-03:00
  
  int years = end.get(Calendar.YEAR) - start.get(Calendar.YEAR);
  int days = end.get(Calendar.DAY) - start.get(Calendar.DAY);
  int hours = end.get(Calendar.HOUR) - start.get(Calendar.HOUR) + days * 24 + years * 365;
  int minutes = end.get(Calendar.MINUTE) - start.get(Calendar.MINUTE);
  
  //...format(HH:mm)
  </code></pre>
  
  <p>I'd prefer to achieve this without having to add an aditional library.</p>