Alexandra, all the different restaurants/bars in DV have slightly different hours that don't vary by month. Here's how they work:
Planet Hollywood (closes around midnight, but it can be later if they're busy)
Annette's Diner - 11pm Sun-Thur, midnight Fri and Sat
King Ludwig's Castle - (provisionally) 11.30pm Sun-Thur, 1am Fri and Sat
Sports Bar - 1am Sun-Thur, 2am Fri and Sat
Billy Bob's - 1am Sun-Thur, 2am Fri and Sat
The Steakhouse - 11am Sun-Thur, midnight Fri and Sat
Rainforest Cafe - 11.30pm
Cafe Mickey - 11pm Sun-Thur, midnight Fri and Sat
McDonald's - midnight
Hurricanes nightclub - 4am.