Hey there, Ona!
I'm so happy to meet you, welcome to planDisney! It looks like your magical vacation is just around the corner, how exciting! I know sometimes it can be confusing to see a special event pop up during your visit, but I'd be happy to give you some more details so you can plan accordingly for a worry-free, "Hakuna Matata" day!
You're correct that
Disneyland After Dark: Throwback Nite is on April 18, 2023. Currently, the park hours listed for Disneyland Park that day are 8:00 AM to 8:00 PM, with the after-hours event continuing beyond the official 8:00 PM closing time.
It's always a good idea to check the calendar and confirm park hours since they're subject to change. You will absolutely be able to enter Disneyland Park that morning (as long as you have a valid ticket and park reservation) and stay until the regular park closing time! Guests of the after-hours event are able to enter Disneyland Park starting at 6:00 PM, so you might find the last couple of hours that day more crowded than usual.
This brings us to the second part of your question: if you purchased
Park Hopper tickets then you can definitely finish your day at Disney California Adventure Park! I especially love seeing
Cars Land with all its glowing neon lights in the evenings. And if you're a thrill seeker then don't miss the
Incredicoaster in the dark!
I think three days is just about the perfect amount of time to explore the parks, Ona.
If you have more questions please feel free to send me a note. I'd be happy to continue our planning together!
Keep moving forward!
Amanda