Never been on a DCL cruise but they do tell you in the description of the cruise you’d like to book if there is a formal night.
Off the top of my head I’d say I doubt it since shorter cruises are designed to pique your interest in cruising with no “ Do I have to wear a jacket?” concerns.
I haven't been on the Magic, but I read that only the longer cruises have formal nights. My first cruise will be on the Wish and there is no formal night at all on that ship because it only does 3 and 4 night trips.
I would say the second night is the "formal" night, unless it's pirate night. It has never been official when I've gone but still the characters dress up
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