Midnight Eastern time. Whatever time that is where you are.
And, you can't log into your reservation until midnight. Already being logged in and clicking "refresh" won't do it.
Be aware, on occasion one window or the other doesn't open at the same time as the other. Sometimes neither opens directly at midnight. The delay can be a few minutes or a few hours. Don't panic. Just keep trying.
GET UP TO A $1000 SHIPBOARD CREDIT AND AN EXCLUSIVE GIFT!
If you make your Disney Cruise Line reservation with Dreams Unlimited Travel you’ll receive these incredible shipboard credits to spend on your cruise!