Hey there Emma,
Welcome to planDisney and thanks so much for this question! I definitely understand that sometimes plans change - luckily it's pretty easy to change your
theme park reservation through the
My Plans hub on the Disneyland Resort website.
It sounds like you're planning on visiting with a 1-day ticket. While it's easy to change your theme park reservation to a different day,
the 1-day tickets do follow a tier system, as you alluded to in your question. Essentially, the higher the tier, the fewer blockout days you need to worry about.
In the event that you switch the day you plan on visiting the Disneyland Resort to a day that requires a higher tier, you'll want to
call a Cast Member at the Tickets line to check on if your current ticket is eligible to be upgraded. If so, they can walk you through the process and how to pay the difference for the higher-tier ticket.
If instead, you plan on visiting on a day that requires a lower-tier ticket then you're already all set! Your current higher-tier ticket is eligible to be used on that tier or any lower-tier day.
Thanks again for your question, Emma! I hope you enjoy your visit to the Happiest Place on Earth.
Have a Magical Day,
Greg