<!DOCTYPE html>
<html>
<body>

Birthday: <input type="date" id="myDate">

<p>Click the button to set the date field to read-only.</p>

<p><strong>Tip:</strong> To see the effect, try to type something in the date field before and after clicking the button.</p>

<button onclick="myFunction()">Try it</button>

<p><strong>Note:</strong> input elements with type="date" do not show as any date field/calendar in Firefox.</p>

<script>
function myFunction() {
    document.getElementById("myDate").readOnly = true;
}
</script>

</body>
</html>