By the time my window came up to book activities the cruise itinerary had MDAS marked, but I'm a first time cruiser and had to wait until 75 days out. Because the activities include MDAS-specific options, though, I'd think they'd display that information for you once you're able to book things.
Anyway, no guarantees but for the 1/21 cruise MDAS is the 2nd day at sea.