Shows are posted on the calendar when we have it confirmed there will actually be a taping that day. It's entirely possible that the taping you want to attend isn't happening. You'll need to wait until the calendar has been posted.
Additionally, it would be pretty unfair to all the other fans if there was a "secret" way of submitting a request early. You'll need to wait, and submit your request when that month's shows are posted on the site.