When trying to determine when to go to Disney, you need to use historic park hours to determine your travel dates to Walt Disney World.
When you go during an off peak time, the Magic Kingdom can close as early as 7 pm cst. Some nights there will be no fireworks. Fantasmic will have infrequent showings. The Animal Kingdom is usually only open from 9 am to 5 pm. And rides are often closed for refurbishment (Splash Mountain for example is usually closed during January every year).
When you go during a peak time, the Magic Kingdom will close as late as 3 am. Some days they will offer Magic Hours at 2 parks instead of one. They really do try their best to accommodate the crowds.
My favorite website for checking the park hours is WDWInfo.com. They have a listing of all the hours that are currently published (Disney releases park hours 180 days in advance) plus hours for the past 18 months. Just pull up the hours for month you plan to travel from the year before. This will give you a general idea of what time the parks will be open when you are considering your dates. Just because a park closes early doesn’t mean you can’t see everything on your list. However, some people’s touring style revolves around being able to stay at the parks late and sleep in.
Considering going to Walt Disney World for Christmas? Read this article about how busy Christmas Day is at Walt Disney World.