duplicate of How to format a JavaScript date
but Marko's accepted answer there for you:
Taken from http://www.webdevelopersnotes.com/tips/html/javascript_date_and_time.php3:
<script type="text/javascript">
<!--
var m_names = new Array("January", "February", "March",
"April", "May", "June", "July", "August", "September",
"October", "November", "December");
var d = new Date();
var curr_date = d.getDate();
var curr_month = d.getMonth();
var curr_year = d.getFullYear();
document.write(curr_date + "-" + m_names[curr_month]
+ "-" + curr_year);
//-->
</script>
You can edit the array to use Jan, Feb, Mar, etc..