I would highly recommend taking a look at datejs. With it's api, it becomes drop dead simple to add a month (and lots of other date functionality):
var one_month_from_your_date = your_date_object.add(1).month();
What's nice about datejs
is that it handles edge cases, because technically you can do this using the native Date
object and it's attached methods. But you end up pulling your hair out over edge cases, which datejs
has taken care of for you.
Plus it's open source!