Hi Maribel, welcome to planDisney!
I completely understand that plans change, but please know that to change your
theme park reservation date from March 17, 2022 to March 18, 2022, you have to cancel your current reservation and book a new one. I just checked the
Theme Park Reservation Availability Calendar and currently March 18, 2022 is fully booked for both
One Park Per day Tickets and Park Hopper Tickets. As such, please do NOT cancel your current reservation just yet. I recommend you keep refreshing the calendar to see if a reservation becomes available for March 18, 2022. Reservations are fluid and constantly changing as Guests can revise their reservations on their own from within their
Disneyland Resort account.
I also want to issue a warning. Even if a reservation for March 18, 2022 were to open up, there is always a chance that the reservation will get booked during the few minutes where you are canceling your current reservation and trying to book a new one. Guests have informed us of this happening, so there is a risk!
With all that said, if you do wish to cancel your current theme park reservation, you'll need to log in to your Disneyland Resort account, select the "My Disneyland" link, and then click the "Ticket and Reservation Details" link. Select the reservation you wish to cancel and click "Cancel Reservation". Once canceled, you're free to go ahead and book your new reservation (based on availability of course).
I hope that helped to clarify! If you have any more questions, please do come back!
See ya real soon!
Jin