Tryit Editor v2.7

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

<input type="date" id="myDate"><br><br>

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

<p><strong>Note:</strong> input elements with type="date" are not supported in Internet Explorer or Firefox.</p>

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

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

</body>
</html>