On of the scenarios is date sensitive and fails if it is run on the first day of a month which is at least as long as the preceding month.

On the server side, I'd just use something like the Ruby timecop plugin to make Date.today return a fixed date for the duration of the test, but in this case it's the jQuery datepicker plugin picking the date and it's just using new Date.

I'm open to suggestions about how to stub things so that I can run this particular scenario 'as if' it was a particular date.