I was on Sea Princess for a week and they had 2 formal nights where people dress up in Tux, dinner suit etc, ladies in cocktail dresses. Other evenings was smart- men suits or shirt and tie, women dresses, smart trousers etc if you are dining in waiter service restaurants. Others were casual if dining in Horizons Court buffet but I dont think they allow jeans/shorts in waiter service restaurants. Mainly -apart from formal nights, -dress as you would at home when going out to a smart restaurant or smart casual. Casual is only for buffet restaurant I think, judging from what I witnessed. However dont forget if your cruise is for more than a week you may have more formal nights- not really a problem for guys but us ladies dont want to wear the same thing! So if you have a lady in your party be sure to let her know! Enjoy your cruise.
Yes dolan is spot on,we've just returned from the very cruise you are taking,which was for fourteen nights you will have 3 formal nights.Of course it is up to you but my wife and i really enjoyed dressing up for these nights,other nights trousers and open neck shirts were abundant,with a few men waring a tie,whilst the ladies all looked wonderful in evening gowns and cocktail dresses,it really was worth that little bit of extra effot.
PS Take something red white or blue for the sailaway out of Gibralta,it was great.
PPS Don't forget the captains cocktails it was a great experiance,what ever you do i am sure you will have a superb time,enjoy your cruise.
Went on the Sea Princess last year, On formal nights my husband wore his £49 Asda suit with white shirt and tie and I wore a cocktail dress, other nights he wore dark trousers with open neck shirt and I wore trousers and a sparkly top. There were many people dressed much more casual so dont worry.