Pop-up Calendar Date format

I have some script (below) which is returning the date from a pop-up calendar. My problem is that the date is being returned in a dd/mm/yyyy format. However I need to be come back with a dd/mm/yy format. Is there anything simple I can do with the code to achieve this.

function y2k(number) { return (number < 1000) ? number + 1900 : number; }

var today = new Date();
var day = today.getDate();
var month = today.getMonth();
var year = y2k(today.getYear());

function padout(number) { return (number < 10) ? '0' + number : number; }

function restart() {
document.accounting.date.value = '' + padout(day) +'/' + padout(month - 0 + 1) + '/' + year;
mywindow.close();

Replace the following line:

var year = year.substring(year.length-2); // pull out right 2 which gives you yy

While the above will work, I prefer the following as JS doesn't have a right() function.

Example: