For reservations done exactly 11-months (home resort) or 7-months (other resort) out from date of arrival, the reservation period starts at 8 a.m. eastern for online reservations. If you are attempting to reserve after the 11/7 month window opens, e.g., if you went online today, October 5, 2023, to reserve a home resort trip with a September 4, 2024 start date, then you can do it online at any time of day, including at midnight (although the system is at times down during the wee hours of the morning due to maintenance). You can also call MS to make the reservation but can only do that when MS is open, starting at 9 a.m.