title: How to subtract time and date
body: <p>I have an ArrayList that has times and dates added like so</p>
  
  <pre><code>06/18/2015 12:25
  06/19/2015 22:45
  </code></pre>
  
  <p>I want to know how can i get the exact time difference in hours between each both date. I have tried</p>
  
  <pre><code>long diff = Math.abs(d1.getTime() - d2.getTime());
  long diffDays = diff / (24 * 60 * 60 * 1000);
  </code></pre>