Hi Danielle,
The following is the list that was released for Extra Magic Hours (Morning and Evening) during December for each park:
December 2008
Morning Extra Magic Hours
Magic Kingdom® Park – December 4, 11, 18, 21-31
Epcot® – December 2, 9, 16, 21, 30
Disney's Hollywood Studios™ – December 6, 13, 20, 22, 26, 28
Disney's Animal Kingdom® Theme Park – December 1, 8, 15, 24, 26-31
Evening Extra Magic Hours
Magic Kingdom® Park – December 1, 8, 15, 21, 26, 28, 30
Epcot® – December 5, 12, 19, 23, 25, 29
Disney's Hollywood Studios™ –December 7, 14, 24, 27, 31
Disney's Animal Kingdom® Theme Park – December 3, 10, 17, 22
I found this list and copied it here for you from Walt Disney World's Website, (www.waltdisneyworld.com). In order to see the operating hours for each park during your stay and what the extended hours would then be given the above information you will need to visit the "Calendar Home Page" which is also located on WDW's website. Just select the park you are interested in and you will see the hours of operation for each day in December. If you then click on the actual day (i.e. December 5, 2008 for Magic Kingdom), then you will see more specific information listed about special events for that actual day as well!
I hope you have a magical stay!
Best wishes,
Brigitta