You cannot make ADR's until the first day of your reservations +180 days out and up to 10 days thereafter. Meaning that you can make reservations for Day 1 at 180 days out, Day 2 at 181 days out, Day 3 at 182 days out, etc. It's considered a "perk" for staying onsite. So for me I can make reservations for December 22nd through December 27th at the 180 day mark which I believe is June 25th.
Quote from wdwinfo "Dining Reservations can be made at all of the Disney World Table Service Restaurants 180 days in advance. Guests staying at a Walt Disney World Resort can make all of their dining reservations for the length of their stay (up to 10 days in advance) at 180 days from their arrival date."
Hope that helps.