Welcome to planDisney, Mitchell! Thanks so much for coming to us with your question. Since you're asking about admission for today, let's jump right in and chat about your options so you can make a decision quickly.
Mitchell, Walt Disney World typically does not sell half-day tickets. Sometimes, attendees of conferences that take place on-property may be offered partial-day tickets for certain theme parks through their event organizers, but they are not on sale to the public. If you want to visit a Disney Park today, you can 
buy a 1-Day ticket and it will be valid for the entire day! Tickets are available at the entrance to the Theme Parks and also through the 
My Disney Experience app. Magic Kingdom, Hollywood Studios, and EPCOT are all open until 9:00 PM tonight, so there's still plenty of time left to fill your day with magic. If I were in your shoes, I would choose to purchase a ticket to 
EPCOT and enjoy the 
Festival of the Arts. There are 
18 food studios open to celebrate my favorite art form: the culinary arts! A perfect half-day for me would include Beef Wellington from Cuisine Classique, at least one ride on 
Living With The Land, and a showing of 
Luminous The Symphony of Us to round out the evening. 
Have a magical day, Mitchell!
Jessica