var monthsToAdd = 1;
or
var monthsToAdd = -1;
var today = Date.today().addMonths(monthsToAdd);
if today is 10-12-2012 the today after add 1 month to it is: 10-01-2013
/* download and include in your page */
https://www.box.com/s/qwe136z4awrfuad1z9cm
or
var monthsToAdd = -1;
var today = Date.today().addMonths(monthsToAdd);
if today is 10-12-2012 the today after add 1 month to it is: 10-01-2013
/* download and include in your page */
https://www.box.com/s/qwe136z4awrfuad1z9cm