Welcome Aboard, Stephanie!
Your cruise is so close, you must be extremely excited! We loved cruising on the Fantasy, and the Eastern Caribbean Itinerary is awesome with three days at sea.
Since my family has sailed the Eastern Caribbean Cruise on the Fantasy, I went into our scrapbook to find your answer. The formal and semi-formal nights are typically on Sea Days, which allows you a little more time in the evening to get ready for dinner. Our formal night was on Sunday, our first sea day, and our semi-formal night was on Thursday, our third sea day.
Like your cruise, our pirate night was also on Tuesday night. All other nights are considered
"cruise casual".
I hope this helps with your cruise packing and planning! Have a fantastic time sailing on the Disney Fantasy. If you have any other questions, I would love to answer them.
Happy Cruising, Tracy V.