Hi there Jenn,
Welcome to planDisney and thanks for your question!
You absolutely can change the date of your visit to the Disneyland Resort, and recently there was a change that made this even easier! For a quick refresher, you need both valid theme park tickets and park reservations for each day of your trip (it sounds like you're just visiting for one day). Before making any changes, I'd first check the
Theme Park Reservation Availability Calendar to ensure the new day that you'd like to visit has reservations available.
Assuming there are available reservations for your new date, you can sign in to your account on
Disneyland.com. After that, you can hover over "My Disneyland" and select "Ticket and Reservation Details." From here, you'll select "Make or Modify Park Reservations," and on the next page, you should see your upcoming theme park reservation. If you select "Modify Reservation" then you'll be able to select your new date. Easy as that!
If you're still running into issues, I'd recommend calling the
Tickets line to speak with a Cast Member who should be able to help.
Thanks again for your question, Jenn! I hope you have a fantastic trip to the Happiest Place on Earth!
Have a Magical Day,
Greg