Hi there, Joliza!
Welcome to planDisney! It's lovely to meet you.
Disneyland Resort park hours can be found online by checking the
daily events schedule. I'm happy to share that Disney California Adventure Park is open on the day you mentioned! However, you must have a valid park ticket and a theme park reservation to enter the park, which I think is probably where you're running into a problem.
Checking the
Theme Park Reservation Availability Calendar, I see that there are no more park reservations available for Disney California Adventure Park if you have a 1 Park Per Day ticket on December 19, 2023. But if you purchase a Park Hopper ticket there are still reservations available!
I also wondered if you might be a Magic Key holder, so I checked the
Magic Key Reservation Calendar. Unfortunately, all theme park reservations for eligible Magic Key holder passes on December 19, 2023, are currently taken.
I totally understand that it's difficult to plan a trip to the parks without knowing you have a park reservation ready to go. You can continue to watch the availability calendars to see if something opens up, but your safest option is to purchase Park Hopper tickets soon and make a park reservation.
Theme park reservations are tough to come by this time of year because the
Holidays at the Disneyland Resort are so magical! I love the seasonal ride overlays, the yummy treats (looking at you, Mickey Gingerbread cookie), and the softly falling snow on Main Street, U.S.A. in the evening. There's really nothing else quite like it! And there's plenty of cheer spread throughout the Downtown Disney District as well, so you can enjoy the festivities even if you don't make it into the parks each day of your visit. A day with a little shopping, exploring the holiday decorations at the Disneyland Resort Hotels, and a great meal sounds pretty magical, too!
I hope you'll be feeling the joy of the season at the Disneyland Resort real soon, Joliza!
Keep moving forward!
Amanda