Anytime dinning is the same on every night. It does not matter if it is formal or not. What you can expect is a large crowd going to eat right after the "party". You can make a reservation on those nights (or for any night) if you wish.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08