Even after they post it you have to keep checking for changes. I've had it happen twice to me where I went off what the website said (the official universal website) before leaving from home for my trip and showed up at the park for early entry only to be told by team members that it is at the other park. And then the team members look at me like I'm crazy. Sometimes they change it after they post it, sometimes the app has it listed wrong, sometimes the app and the website list different things.
It's a fun guessing game...… If you are staying at a universal hotel I highly recommend asking the hotel at check in for confirmation of park hours.