Web countdown

html JavaScript 
<head>
  <style>
    html,
    body {
      height: 100%;
      width: 100%;
      margin: 0;
      padding: 0;
    }

    body {
      display: grid;
      place-items: center;
    }
  </style>
</head>
<body>
  <H1>DM in : <span id="datetime"></span></H1>
  <script>
    let dateTimeUTC = new Date("2022-01-01T00:00:00.000Z"); // UTC date time form ISO
    setInterval(
      () => {
        let dateTimeNowUTC = new Date();
        let isPast = dateTimeUTC.getTime() < dateTimeNowUTC.getTime();
        let dateTimeDiffPast = new Date(dateTimeNowUTC - dateTimeUTC);
        let dateTimeDiff = new Date(dateTimeUTC - dateTimeNowUTC);

        let currentDateTimeDiff = isPast ? dateTimeDiffPast : dateTimeDiff;

        let year = 1970 - currentDateTimeDiff.getUTCFullYear();
        let month = currentDateTimeDiff.getUTCMonth();
        let day = 1 - currentDateTimeDiff.getUTCDate();
        let hours = currentDateTimeDiff.getUTCHours();
        let minutes = currentDateTimeDiff.getUTCMinutes();
        let seconds = currentDateTimeDiff.getUTCSeconds();

        let str = Math.abs(year) + "y " + Math.abs(month) + "m " + Math.abs(day) + "d " + Math.abs(hours) + ":" + Math.abs(minutes) + ":" + Math.abs(seconds);
        document.querySelector("#datetime").innerHTML = isPast ? "+" + str : str;
      },
      1000
    );
  </script>
</body>

DM in :