Runnable,uptimeMillis,postAtTime

private Runnable mUpdateTimeTask = new Runnable() {
   public void run() {
       final long start = mStartTime;
       long millis = SystemClock.uptimeMillis() - start;
       int seconds = (int) (millis / 1000);
       int minutes = seconds / 60;
       seconds     = seconds % 60;

       if (seconds < 10) {
           mTimeLabel.setText("" + minutes + ":0" + seconds);
       } else {
           mTimeLabel.setText("" + minutes + ":" + seconds);            
       }
     
       mHandler.postAtTime(this,
               start + (((minutes * 60) + seconds + 1) * 1000));
   }
};