International Harry Potter Day Event Details Starts: April 29, 2017 @ 10:00 amEnds: April 29, 2017 @ 2:00 pm J.K. Rowling has inspired millions of young readers with series character, Harry Potter. Celebrate International Harry Potter Day by mixing scientific potions, battling in a Quidditch game, or choosing your pathway to the Slytherin serpents or glorious Gryffindor lions with the Sorting Hat! Children and adults will be inspired by the literary, fantastical world of Harry Potter and other characters! Costumes are encouraged. Included with general admission or museum membership.