From my email confirmation...pertinent parts. So if I have a reservation for Wednesday, in my opinion I would cancel by Monday to be 100% sure I am not within the "one day of the reservation". I would consider Tuesday to be within one day.
Payment and Cancellation Policies
~Payment or credit card guaranty is required at the time of booking.
~At time of booking, payment in full must be charged to a valid credit card or, if on a dining package, there must be a guaranty to a valid credit card. If you fail to show for this priority seating and do not cancel your reservation, your card will be charged a penalty.
~There is a one-day cancellation policy and a full price charge if you cancel within one (1) day of the reservation or are a "no show" for the reservation.