Yes they do have an optional formal night for those who like to take part, as the advert says you are free to do whatever i should imagine they have 3-4.
I thought NCL did not do formal. Is it not dress as you like.
Yes, I know you don't have to dress up, but I thought there were a few days where they had formal evenings, perhaps I am wrong!
As many or as few as you want if you feel like dressing up then its ok most of the restaurants have a dress code so jeans aren’t allowed but otherwise it up to you.
Wearing formal clothing is entirely optional. Call 1-866-7350 for confirmation.