You can book a room (room only, not a package) as far out as 499 days. So today (3/8/19) you could book a room for as far out as July 19, 2020.
You will be required to put down a deposit of 1 night's room and taxes. The rate for the deposit will be the current rack rate (in this example, it'll be the 2019 rate since 2020 rates have not yet been released). Once the actual rates are released, you will be expected to add to your down payment to bring it up to whatever the 2020 is for that one night.
Steve