T.H.
I would shorten his naps and make sure he is eating every 4 hours at the very least (don't let him go more than 4 hours). It sounds as though he may be trying to get his days and nights turned around. It also could be due partially to the time change, it messes with kids. Good luck.
I just looked through some of the responses you received and I would strongly disregard that of Jesse when she said that 6 hours is unrealistic both of my kids slept 6 plus hours straight at night from about the time they were 4 months old on. You should be able to get sleep and your baby should as well. I don't suggest using blankets in the crib just make sure the room is about 70 degrees and I have a radio in both of my kid's rooms and yes, they are addicted to having music on at night when going to bed but it helps them sleep. I usually have something light and relaxing playing all night and then I get the added benefit of hearing it through the baby monitor. If you cut out that third nap and shorten the naps (maybe one 2 or 3 hour nap and 1 1 - 2 hour nap) that should help a lot. It sounds as though he is getting a majority of his required sleep during the day.