Structure

library_books<p>Time left for <br><b>Feb 22, 2020, 8:30:30AM</b></p>
 <br><br>
<h1 id="timer"></h1>

Process

library_books<script type="text/javascript">
// Set the date we're counting down to
var countDownDate = new Date("Feb 22 2020 8:30:30").getTime();
var aSecond=1000,
    aMinute=aSecond*60,
    anHour=aMinute*60,
    aDay=anHour*24;
// Update the count down every 1 second
var countdown = setInterval(function() {

  // Get todays time in milliseconds
  var now = new Date().getTime();

  // Time difference between now and the count down date
  var timeDifference = countDownDate - now;

  // Time calculations for days, hours, minutes and seconds
  var days = Math.floor(timeDifference / aDay);
  var hours = Math.floor((timeDifference % aDay) / anHour);
  var minutes = Math.floor((timeDifference % anHour) / aMinute);
  var seconds = Math.floor((timeDifference % aMinute) / aSecond);

  // Output the result
  document.getElementById("timer").innerHTML = days + "d : " + hours + "h : "
  + minutes + "m : " + seconds + "s ";

  // Message to show after the count down over
  if (timeDifference < 0) {
    clearInterval(countdown);
    document.getElementById("timer").innerHTML = "DATE EXPIRED";
  }
}, 1000);
</script>