We're going on the Carnival Liberty, too. The formal nights are the nights of the days at sea, which makes it Sunday & Friday nights. (When the person said 2 & 7 it might have been a little confusing).
I'm looking forward to a great time. Was to San Juan, St. Thomas & the Bahamas last year on another ship. looking forward to Antigua & Tortola. Already booked the Royal Swim with the Dolphins at dolphindiscovery.com in Tortola.