title: Change device timezone to GMT in android
body: <p>"13-11-2012 09:14:39" is the sample timestamp string getting from server in my app. I need to calculate the defference between that time and current device time. 
  My Server is sending the time in GMT format. Do i need to change the device timezone to GMT to calculate current time in GMT? And how can i get exact diff b/w those two times. Please help me.<br>
  Here is what i have tried so far:</p>
  
  <pre><code>SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy hh:mm:ss");
  
  Date requestDate = formatter.parse(serverDateString);
  
  Calendar requestDateCal = formatter.getCalendar();
  requestDateCal.setTime(requestDate);
  
  Calendar currentDateCal = Calendar.getInstance();
  calculateTimeDiff(currentDateCal.getTimeInMillis(), requestDateCal.getTimeInMillis()); //finds diff between two timestamps
  </code></pre>