I had a trip once where the hours were changed after we got there, about 5 years ago. The World Update we got at check-in had different hours than when we went to the park. We went to MK and I had some kind of special card that we could get preferred fireworks viewing, I went to City Hall first thing in the morning to sign up. It was then that the cm told me that the electrical parade and fireworks were 30 minutes earlier than the schedules said! Turned out there was a thunderstorm, the electrical parade was cancelled and we didn't even go to the special fireworks viewing area because it was still raining (but the fireworks did go off).