I have an input form which looks like this:

<input type="time" id="myTime" value="00:00">
<button onclick="myFunction()">Here</button>

<script>
function myFunction() {
  document.getElementById("myTime").stepDown(30);
}
</script>

Scenario:

I would like to stepDown(30) for 12:00 am. The expected result I should get is 11:30pm, but the value doesn't change. Is there any reason?