Помогите сделать таймер циклическим

console.clear();


function CountdownTracker(label, value) {

  var el = document.createElement('span');

  el.className = 'flip-clock__piece';
  el.innerHTML = '<b class="flip-clock__card card"><b class="card__top"></b><b class="card__bottom"></b><b class="card__back"><b class="card__bottom"></b></b></b>' +
    '<span class="flip-clock__slot">' + label + '</span>';

  this.el = el;

  var top = el.querySelector('.card__top'),
    bottom = el.querySelector('.card__bottom'),
    back = el.querySelector('.card__back'),
    backBottom = el.querySelector('.card__back .card__bottom');

  this.update = function(val) {
    val = ('0' + val).slice(-2);
    if (val !== this.currentValue) {

      if (this.currentValue >= 0) {
        back.setAttribute('data-value', this.currentValue);
        bottom.setAttribute('data-value', this.currentValue);
      }
      this.currentValue = val;
      top.innerText = this.currentValue;
      backBottom.setAttribute('data-value', this.currentValue);

      this.el.classList.remove('flip');
      void this.el.offsetWidth;
      this.el.classList.add('flip');
    }
  }

  this.update(value);
}

// Calculation adapted from https://www.sitepoint.com/build-javascript-countdown-timer-no-dependencies/

function getTimeRemaining(endtime) {
  var t = Date.parse(endtime) - Date.parse(new Date());
  return {
    'Total': t,
    'Days': Math.floor(t / (1000 * 60 * 60 * 24)),
    'Hours': Math.floor((t / (1000 * 60 * 60)) % 24),
    'Minutes': Math.floor((t / 1000 / 60) % 60),
    'Seconds': Math.floor((t / 1000) % 60)
  };
}

function getTime() {
  var t = new Date();
  return {
    'Total': t,
    'Hours': t.getHours() % 12,
    'Minutes': t.getMinutes(),
    'Seconds': t.getSeconds()
  };
}

function Clock(countdown, callback) {

  countdown = countdown ? new Date(Date.parse(countdown)) : false;
  callback = callback || function() {};

  var updateFn = countdown ? getTimeRemaining : getTime;

  this.el = document.createElement('div');
  this.el.className = 'flip-clock';

  var trackers = {},
    t = updateFn(countdown),
    key, timeinterval;

  for (key in t) {
    if (key === 'Total') {
      continue;
    }
    trackers[key] = new CountdownTracker(key, t[key]);
    this.el.appendChild(trackers[key].el);
  }

  var i = 0;

  function updateClock() {
    timeinterval = requestAnimationFrame(updateClock);

    // throttle so it's not constantly updating the time.
    if (i++ % 10) {
      return;
    }

    var t = updateFn(countdown);
    if (t.Total < 0) {
      cancelAnimationFrame(timeinterval);
      for (key in trackers) {
        trackers[key].update(0);
      }
      callback();
      return;
    }

    for (key in trackers) {
      trackers[key].update(t[key]);
    }
  }

  setTimeout(updateClock, 500);
}

var deadline = new Date(Date.parse(new Date()) + 12 * 24 * 60 * 60 * 1000);
var c = new Clock(deadline, function() {
  alert('countdown complete')
});
document.body.appendChild(c.el);

var clock = new Clock();
document.body.appendChild(clock.el);

html {
  height: 100%;
}

body {
  min-height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  background: #EEE;
}

.flip-clock {
  text-align: center;
  perspective: 400px;
  margin: 20px auto;
  *,
  *:before,
  *:after {
    box-sizing: border-box;
  }
}

.flip-clock__piece {
  display: inline-block;
  margin: 0 5px;
}

.flip-clock__slot {
  font-size: 2vw;
}

@halfHeight: 0.72em;
@borderRadius: 0.15em;
.card {
  display: block;
  position: relative;
  padding-bottom: @halfHeight;
  font-size: 9vw;
  line-height: 0.95;
}

.card__top,
.card__bottom,
.card__back::before,
.card__back::after {
  display: block;
  height: @halfHeight;
  color: #ccc;
  background: #222;
  padding: 0.25em 0.25em;
  border-radius: @borderRadius @borderRadius 0 0;
  backface-visiblity: hidden;
  transform-style: preserve-3d;
  width: 1.8em;
  transform: translateZ(0);
}

.card__bottom {
  color: #FFF;
  position: absolute;
  top: 50%;
  left: 0;
  border-top: solid 1px #000;
  background: #393939;
  border-radius: 0 0 @borderRadius @borderRadius;
  pointer-events: none;
  overflow: hidden;
}

.card__bottom::after {
  display: block;
  margin-top: -@halfHeight;
}

.card__back::before,
.card__bottom::after {
  content: attr(data-value);
}

.card__back {
  position: absolute;
  top: 0;
  height: 100%;
  left: 0%;
  pointer-events: none;
}

.card__back::before {
  position: relative;
  z-index: -1;
  overflow: hidden;
}

.flip .card__back::before {
  animation: flipTop 0.3s cubic-bezier(.37, .01, .94, .35);
  animation-fill-mode: both;
  transform-origin: center bottom;
}

.flip .card__back .card__bottom {
  transform-origin: center top;
  animation-fill-mode: both;
  animation: flipBottom 0.6s cubic-bezier(.15, .45, .28, 1); // 0.3s; 
}

@keyframes flipTop {
  0% {
    transform: rotateX(0deg);
    z-index: 2;
  }
  0%,
  99% {
    opacity: 0.99;
  }
  100% {
    transform: rotateX(-90deg);
    opacity: 0;
  }
}

@keyframes flipBottom {
  0%,
  50% {
    z-index: -1;
    transform: rotateX(90deg);
    opacity: 0;
  }
  51% {
    opacity: 0.99;
  }
  100% {
    opacity: 0.99;
    transform: rotateX(0deg);
    z-index: 5;
  }
}