Many mistakes
1. In the body tag () brackets are missing.
2. For TextBox you made use of innerHTML, but it has value.
3. For Label you made use of jQuery but the jQuery is not inherited.
From above it seems you don't have knowledge of client side scripting thus spent some time learning basics and syntax
Correct code is below
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body onload="ClientTime()">
<script type="text/javascript">
function ClientTime() {
var dt = new Date();
var ss = dt.getSeconds();
var mm = dt.getMinutes();
var hh = dt.getHours();
var timeNow = 'Time is:' + hh + ':' + mm + ':' + ss;
document.getElementById('txtName').value = timeNow;
document.getElementById('datediv').innerHTML = timeNow;
}
</script>
<span id="datediv"></span>
<input id="txtName" name="txtName2" type="text" value="Test" />
</body>
</html>
Demo
