codice:
<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>countdown test</title>
  <style>
    #countdown {
      display: flex;
    }

    .endcountdown {
      text-decoration: line-through;
    }
  </style>
</head>

<body>

  <div id="headline"></div>
  <div id="countdown"></div>

  <script>

    const headline = document.getElementById("headline")
    const countdown = document.getElementById('countdown')
    const future = Date.parse("jun 15, 2022 19:46:59")

    function updateTimer() {
 
      const now = new Date()
      const diff = future - now
      const days = Math.floor(diff / (1000 * 60 * 60 * 24))
      const hours = Math.floor((diff / (1000 * 60 * 60)) % 24)
      const minutes = Math.floor((diff / 1000 / 60) % 60)
      const seconds = Math.floor((diff / 1000) % 60)

      if (diff < 0) {
        headline.textContent = "Evento in corso!"
        countdown.textContent =
          `0 Giorni
          0 Ore
          0 Minuti
          0 Secondi
       `
        countdown.classList.add('endcountdown')
        clearInterval(CountDownTimer)
      } else {
        countdown.textContent =
          `${days} Giorni
          ${hours} Ore
          ${minutes} Minuti
          ${seconds} Secondi
       `
      }
    }

    const CountDownTimer = (() => setInterval(updateTimer, 1000))()

  </script>

</body>

</html>