This code show cowntdown timer clock - JavaScript

countdown-timer.html

<!-- This display the countdown timer clock in an element -->
<p id="timer"></p>

<script>
//Put here the time and date when it will stop ("Sep 17, 2020 15:37:25")
var countdowndate = new Date("Sep 17, 2020 15:37:25").getTime();
var x = setInterval(function() {
  var now = new Date().getTime();
  var timecal = countdowndate - now;
  var days = Math.floor(timecal/(1000*60*60*24));
  var hours = Math.floor((timecal%(1000*60*60*24))/(1000*60*60));
  var minutes = Math.floor((timecal%(1000 * 60 * 60))/(1000 * 60));
  var seconds = Math.floor((timecal%(1000*60))/1000);
  document.getElementById("timer").innerHTML = days + "d " + hours + "h "
  + minutes + "m " + seconds + "s ";
  if (timecal<0) {clearInterval(x);document.getElementById("timer").innerHTML = "expire";}},1000);
</script>