Grad night is held in California Adventure which typically closes at either 8 or 9. I do not know where you got your information, but June 14th is NOT a grad night. June 9th is the last grad night this year. You can always look on Disneylands website for park hours, event schedules, and more. Hope this helps. :)
I don't think grad nights affect the park hours, I was there yesterday and they have their regular schedule and the grads can be in the park all day and stay after the park closes to the public.
The park will be closing early on June 14th for Grad Nite. Grad Nite closes off the park to the students from 10pm to 2am. So Disneyland will be closing two hours early. If you arrive early you have the best chance of getting on the most attractions without the teens to bug you. Most of the teens arrive in the early to late afternoon for Grad Nite.
Will California Adventure close early as well, I know grad nite is only at the main park. I drove by a HS in orange and they had grad night as the 14th. Maybe I need to check out the Disney site. Thanks
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