public static String formatTimeDiff(long last) {
		long time = System.currentTimeMillis() - last;	
		
		final int sec = (int) (time / 1000), h = sec / 3600, m = sec / 60 % 60, s = sec % 60;
		return (h < 10 ? "0" + h : h) + ":" + (m < 10 ? "0" + m : m) + ":"
				+ (s < 10 ? "0" + s : s);
	}