index.html

<!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>Timer</title>
    <link rel="stylesheet" href="style.css" />
  </head>
  <body>
    <div class="box">
      <form class="setDateTime">
        <input
          type="datetime-local"
          name="datetime"
          value="datetime"
          id="datetime"
        />
        <button type="submit" id="submit">submit</button>
      </form>
      <table style="width: 80%; height: 3rem">
        <tr>
          <td id="">days</td>
          <td id="">hour</td>
          <td id="">minute</td>
          <td id="">second</td>
        </tr>
        <tr
          id="timeRow"
          style="font-size: larger; font: 500 bold; height: 2rem"
        >
          <td id="days"></td>
          <td id="hour"></td>
          <td id="minute"></td>
          <td id="second"></td>
        </tr>
      </table>
    </div>
  </body>
  <script src="script.js"></script>
</html>