The park operating hours and Extra Magic Hours schedule has been significantly changed in a recent calendar update.
Most evening Extra Magic Hours at the Magic Kingdom have been moved to different days from mid-July onwards, along with morning Extra Magic Hours at Disney's Animal Kingdom. Both parks have also seen significant extensions to park hours, and at the Magic Kingdom, an increase in the number of Main Street Electrical Parade performances.
Disney's Hollywood Studios has also seen changes to EMH days, and a lot of extensions to regular operating hours and additional Fantasmic! shows.
Epcot appears to have escaped any changes so far.
If you are planning, or already have a trip planned, you should double check the calendar for any changes that may impact your trip. We have an easy to use calendar at http://www.wdwmagic.com/calendar.htm, and you can also view the official calendar at http://www.disneyworld.com.