I don't think there's a specific time, but I think it usually happens by 5:00 a.m. eastern time. I know that anytime a discount has been released for a time we're traveling, our TA has sent me an email by 6:00 a.m. letting me know she applied the discount and modified our reservation. I think the
free dining deal dropped before 4:00 a.m. last week because she mentioned to me that by 6:30 a.m. she had modified all of her client reservations and that she had been up for over 3 hours at that point.