It depends - sometime you have to call.
The web tool has historically gotten the next year's rates around June (they were early this year but could be due to the pandemic). For example, around June 2017 is when the rates for 2018 were set and you could book 2018 online (out to the 500 day/499 night limit).
The issue had been that if you wanted to book 2018 in MAY 2017, the online tool couldn't do it. So they only way to do it was to call and book 2018 and Disney would make a reservation based on the same time frame for 2017 rates and charge you a deposit. But once 2018 rates were announced, those 2018 rates would replace what's in your reservation. Your deposit, since already paid, would net out against the total 2018 cost and you would owe the difference. You don't LOCK IN the old rates. You accept a spot holding your place and agree to pay whatever the rates are when they are released.
Where we are now in late September 2021, you can book online to the end of 2022. But the 500 day would take you into early February 2023. The only way to get a Jan-Feb 2023 reservation NOW is to call, get a quote based on 2022 rates, pay a deposit, then those rates will update once we get to June 2022 (or whenever they update rates). You can't even see Jan 2023 dates in the online tool.
Hope this is clear enough, Mike.
Bama Ed
PS - when you have to call, you know you get the old year's rates and expect to pay up to 10% more for year-over-year increases (assuming rate periods don't change - like the Easter holiday time).