Using new Date(number), creates a new date object as
zero time plus the number. Zero time is 01 January 1970 00:00:00 UTC. The number is specified in milliseconds:
HTML file:
Displayed by browser:
<body>
<p id="demo"></p>
<script>
var d = new Date(86400000);
document.getElementById("demo").innerHTML = d;
</script>
</body>
JavaScript dates are calculated in milliseconds from 01 January, 1970 00:00:00 Universal Time (UTC). One day contains 86,400,000 millisecond.