We just were on the 1/22/05 Eastern. Formal Night is Sunday. Semi-Formal is Thursday. We had APL rotation, so we were in Lumiere's on Monday & Thursday. We had Wednesday at Palos. As a result, the 9 adults in our party wore at least semi-formal for Sunday night, Thursday night and Wednesday at Palos. We decided to do casual dinner wear (dockers, polo shirts, etc.) for Lumiere's on Monday night vs. 4 nights of dressing up. We certainly didn't feel out of place in Lumiere's with business casual on Monday, but I certainly recommend dressing for the formal, semi-formal and Palo dinners.
Pirate night is on Tuesday after day at St. Maartan. It's casual dinner wear. A few guests wear eye patches or pirate hats to dinner, but nothing to outlandish. Regardless, you'll receive a pirate dew (sp?) rag at dinner to wear and most guests went this route. They've had some complaints I guess that Pirate night is after a long day in St. Maartan, starts at 9:45pm w/fireworks not going off until 10:45ish, then the next day in St. Thomas it's mandatory that everyone on the ship get up by 6:30 or 7:00am to go through the U.S. Customs check in the Walt Disney Theatre. However, the reasoning makes sense, as it's the only time that the ship isn't on a rushed schedule and the captain can take time to position the ship so the wind carries the fireworks away from the ship.