Hi Amy,
Thank you so much for visiting the Disney Parks Moms Panel with your question. We on the panel love helping guests to plan magical vacations!
When you visit Walt Disney World, you can only use one day of
theme park admission per day. You cannot use two days of theme park admission to visit two different theme parks on one day. The only way to visit more than one theme park per day is to purchase the Park Hopper Option, which allows you to move between theme parks on the same day.
Perhaps if you already have more days worth of theme park admission than you were planning to use, if you are arriving late in the afternoon the day before you planned to go to the theme parks, or if you are leaving midday on your last day and had not planned to go to the theme parks, now you can go on one of those days. You could start or end your vacation with a meal and first or final attraction at a theme park!
I hope that this information is helpful for you, Amy. Please do let us know if you have any further questions.