There are Fireworks on Grad Nights, but only for the Grad Night participants, in past these have been around midnight (unless you want to watch from somewhere outside the park) they do not do fireworks during regular park hours due to the early close and the set up time for the things involved with Grad Night.
As for April 22 to my understanding from the other thread it was a park wide buy out for the McDonalds Convention. On that day there are no scheduled fireworks for regular park operating hours. If there will be any during the McDonald's event, I don't know as it is additional cost to the company and some conventions do have them, others don't.