The summertime is one of the best times of the year to catch carp after dark. Yes, they do hit after dark and they hit well. Take a look at the mirror at right that I landed a couple of nights ago. In the summer and early fall carp have a tendency to leave deep water daytime lairs and move closer to shore to roam around and feed under cover of darkness. I can't tell you how many times I am sitting in a chair tending my rods after dark and when I go to get up I suddenly startle a large carp that is sitting in just inches of water right in front of me. Another plus (or minus as some see it) is that you have a shot at catching horned pout or large catfish (channels and whites) after dark. They hit the same baits as carp do.
If you do try nighttime carp fishing, I would strongly advise that you try to pick an area that is safe and secure. And, bring along lights and lots of bug spray.