(Look at your fun days at sea, they will be on those evenings....)
Not necessarily..... All 3 previous cruises I have been on had formal nights on port days. This includes the following:
Fascination - 2nd day (Key West)
Triumph - 5th day (Grand Cayman)
Sensation - 2nd day (Nassau)
In addition, on my upcoming cruise on the Glory, I have been advised that the first formal night is the 2nd day. Again, I will have been in Nassau that day.