Djokovic played a night match against Baghdatis in the 4th round on this last AO that finished at 3 am. Just one example.I think no national tennis fan is classy when it comes to their own playing on court in a huge match. A good example of this is any Davis Cup match. Had there been a GS in Serbia or Spain, I am sure they would get pretty unfair too in some matches.
I believe they are evening matches. So e.g. they start at 7 PM. USO matches can start at 10 PM or whoever late they need to.