There is no list that I have ever seen of "Seasonal Attractions". As for when they operate, there is no telling. Some of them have never reopened (after going seasonal) some have only been open once or twice. You will find attractions like Carousel of Progress and the Timekeeper at Magic Kingdom do actual open "seasonally" as stated (around easter and winter holidays...and if something else is closed for rehab in Tomorrowland), but then there are also attractions like the Keelboats (MK) that is a "Seasonal" attraction that has never reopened since it stop running on a daily basis...