<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<h1 id="the_numbers">0</h1>

<script>
var output = $('h1');
var isPaused = false;
var time = 0;
var t = window.setInterval(function() {
if(!isPaused) {
time++;
var time_60_mod = time%60;
document.getElementById('the_numbers').innerHTML = Math.floor(time / 3600)%24 + ":" + Math.floor(time / 60)%60 + ":" + time_60_mod.fadeOut(500);
time_60_mod.fadeIn(500);
}
}, 1000);

</script>