In Masters 1000 events 1 semi is always during a day and the other one is at night. It's been like that for a long time. In 2012 in Toronto, the 2nd semi final was also interrupted by rain so Nole won that match well after 11 pm and had to come back the next day to play the final in the afternoon. There are numerous cases like that. Federer has been playing all of his matches at night, which probably helps to avoid the sunshine and heat during day, but it does affect a little bit if he makes the final. I am sure that with his conditioning, it won't be a huge problem. It is best of 3 match and players are used to it.
Does anybody know why Andy's girlfriend is not with him in North America? I didn't see her in Toronto and she wasn't shown on TV last night also so I assume she is not there.