This is from their website:
"Casual resort wear is appropriate at any time.
After 6:00pm, jeans, t-shirts, shorts, and bare feet are not permitted in the ships' public areas.
A cocktail dress for women and a suit or coat and tie for men are appropriate on formal evenings (one on 4- to 6-night cruises, two on 7- to 11-night cruises, and four on cruises 15 nights or longer)." So no shorts and jeans after 6pm.