Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<body>

<input type="time" id="myTime"><br><br>

<button onclick="disableBtn()">Disable Time Field</button>
<button onclick="undisableBtn()">Undisable Time Field</button>

<script>
function disableBtn() {
    document.getElementById("myTime").disabled = true;
}

function undisableBtn() {
    document.getElementById("myTime").disabled = false;
}
</script>

</body>
</html>