2018-08-15_page was loaded this much seconds ago

<!DOCTYPE html>
<html>
<body>

<p>This page was loaded <span id="demo"></span> seconds ago.</p>

<input type="hidden" id="savetime" value="">

<button onclick="clearInterval(myVar)">Stop time</button>

<script>
    var d = new Date();
    var p = Math.floor(d.getTime()/1000);
    document.getElementById("savetime").value = p;
    var myVar = setInterval(myTimer ,1000);

    function myTimer()
    {
        var x = document.getElementById("savetime").value;

        var d = new Date();
        var p = Math.floor(d.getTime()/1000);

        var tago = Number(p) - Number(x);

        document.getElementById("demo").innerHTML = tago.toString();
// Remark : timeAgo type script.
    }
</script>

</body>
</html>