Update setInterval
HTML
<div><script>document.getElementById(time);</script></div>
JavaScript
function writeDate () {
var today = new Date();
time.innerHTML = "The time now is: " + today.getHours() +":" + today.getMinutes() + ":" + today.getSeconds();
time.innerHTML += "<br>The date is: " + today.getDate() + "/" + (today.getMonth() + 1) + "/" + today.getFullYear();
}
setInterval(writeDate, 1000);