Hi Keith! Welcome to planDisney! Thanks so much for stopping by and sending us your question. I'm happy to help!
How fun that you're arriving at 
The Happiest Place on Earth in just one day! You can cancel your existing 
theme park reservation and make a new one pending availability. I recommend checking the 
Theme Park Reservation Availability Calendar first to see if the date you would like to visit is available to reserve. If it's an 
advanced dining reservation you would like to change, you can cancel up to two hours before your reservation, depending on the dining location and experience. Some prepaid dining experiences such as the 
World of Color Dessert Party must be canceled at least one day before your reservation to get a refund. Reservations cannot be modified and must be canceled if you want to change the date.
If you plan to be at 
Disneyland Park and are a football fan, you might see the newest Super Bowl champs parading down 
Main Street, U.S.A.! During your visit, you can also look forward to the 
Disney100 Celebration. I wish you a magical visit and hope you will stop by 
planDisney again. We would love to help you! 
See ya real soon!
Smiles,
Lisa