It runs from 7:00 to midnight. And Mickey_Maniac, we'll see you there on the 19th! Judging by your other posts, your itinerary sounds REALLY similar to ours!
Banshee, you might want to see if you can move up your PS to maybe 5:00 or 5:30. If you can't get Chef Mickey's at that time, try Crystal Palace or Liberty Tree. They've all probably been booked solid already, but there's always the chance of a cancellation.
If you can't change your PS, I'd opt to cancel it and try to work in Chef Mickey's on another night. Otherwise, you probably wouldn't even be in the MK before 7:45 or so. Lines for photos and treats would already be long, and good spots for the 8:00 parade would already be taken.