<!DOCTYPE html>
<html>
<body>
Time: <input type="time" id="myTime" value="16:32:55">
<p>Click the button to change the default value of the time field.</p>
<button type="button" onclick="myFunction()">Try it</button>
<script>
function myFunction() {
document.getElementById("myTime").defaultValue = "18:00";
}
</script>
</body>
</html>