best time to hunt is.... the whole day if you can. i've seen big bucks at all times of the day. that being said, when pre-rut and the rut are going on, mid day activity increases. deer eat 4-5 times a day, twice during the night, at dawn and dusk, and once mid-day. alot of their feeding patterns change when rutting activity starts. when it's not the rut, even if deer are more nocturnal they still feed at least once during the day, and the dawn and dusk feeding times move an hour or so earlier and later, so it's hard to see them or get a shot at them. so all this being said, mid-day hunting can always be good. best bet though is to do what i started this post with..... hunt all day
most of the time i don't because i like to come in and eat, shower, take a nap, play with the dog or whatever. but when the ruts starting i'm out there alot more often and longer hunts