The following is from the Carnival web site ...
How many formal nights are there?
For cruises with one formal night, the formal night is scheduled for the second or third evening of the cruise, with schedules permitting. For cruises with two formal nights, the first formal night is scheduled for the second or third evening of the cruise; the second formal night is scheduled for the second or third evening prior to the end of the cruise, with schedules permitting.
1-day cruise: no formal nights
2-day cruise: one formal night
3-day cruise: one formal night
4-day cruise: one formal night
5-day cruise: one formal night
6-day cruise: two formal nights
7-day cruise: two formal nights
8-day cruise: two formal nights
9-day cruise: two formal nights
10-day cruise: two formal nights
11-day cruise: two formal nights
12-day cruise: two formal nights
13-day cruise: two formal nights
14-day cruise: two formal nights
16-day cruise: two formal nights
17-day cruise: two formal nights
