We can fix the month and day part of date object by using setmonth JavaScript function. We can set the month from 0 to 11. In this January month is taken as 0 month and December is taken as 11.
dateobject.setMonth(month,day)
Sample code is here
<script type="text/javascript">
var dt= new Date();
document.write(dt + "<br><br>");
dt.setMonth(3,5);
document.write(dt);
</script>
The output of above code
Try to change the month beyond 11 and see how the year part also change. Change this like this.