Vanilla JS countdown timer to specific date

countdown-timer.html

<div class="countTimer" data-date="01 Jan 2030 00:00:00 GMT">
  <div class="countdown-wrapper">
    <div class="countdown-cell">
      <span class="timer-number tDays">00</span>
      <div class="timer-caption">Days</div>
    </div>
    <div class="countdown-cell">·</div>
    <div class="countdown-cell">
      <span class="timer-number tHours">00</span>
      <div class="timer-caption">hours</div>
    </div>
    <div class="countdown-cell">·</div>
    <div class="countdown-cell">
      <span class="timer-number tMinutes">00</span>
      <div class="timer-caption">Minutes</div>
    </div>
    <div class="countdown-cell">·</div>
    <div class="countdown-cell">
      <span class="timer-number tSeconds">00</span>
      <div class="timer-caption">Seconds</div>
    </div>
  </div>
</div>
<script>
  function addZeroToOutput(num) {
    let output = num < 10 ? '0' + num : num;
    return output;
  }
  let countdownTimers = document.querySelectorAll('.countTimer');
  countdownTimers.forEach(function(timer) {
    let daysEl = timer.querySelector('.tDays');
    let hoursEl = timer.querySelector('.tHours');
    let minutesEl = timer.querySelector('.tMinutes');
    let secondsEl = timer.querySelector('.tSeconds');
    let deadlineDate = new Date(timer.dataset.date);

    let second = 1000,
      minute = second * 60,
      hour = minute * 60,
      day = hour * 24;

    let countDown = new Date(deadlineDate).getTime(),
      x = setInterval(function() {
        let now = new Date().getTime(),
          distance = countDown - now;
        daysEl.innerText = addZeroToOutput(Math.floor(distance / (day))),
        hoursEl.innerText = addZeroToOutput(Math.floor((distance % (day)) / (hour))),
        minutesEl.innerText = addZeroToOutput(Math.floor((distance % (hour)) / (minute))),
        secondsEl.innerText = addZeroToOutput(Math.floor((distance % (minute)) / second));
        if (distance < 0) {
          countdownTimers.parentNode.removeChild(countdownTimers);
          clearInterval(x);
        }
      }, 1000);
  });
</script>