Formal night on sensation

is there a formal night on the three night cruise Oct 29th on the Sensation

Yes, probably, but its hardly formal any more. Carnival calls it 'Elegant night" now. This means you can dress up IF you want to but don't have to. There are very few tuxes, men are more apt to wear a suit, if that. Woman tend to dress more formally but you see very few beaded gowns if any.

We have seen shorts and jeans on what used to be formal nights- UGH!

Formal isn't really formal anymore. just dress nicely and you will be fine.