Try with below code:
<html>
<body>
<table border="1" cellpadding="0" cellspacing="0">
<tr>
<th>
StudentName
</th>
<th id="monthName">
</th>
</tr>
<tr>
<td>
Manas
</td>
<td>
1000
</td>
</tr>
</table>
<script>
var month = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
var d = new Date();
var n = month[d.getMonth()];
document.getElementById("monthName").innerHTML = n;
</script>
</body>
</html>