J.G.
My son was the same way. He was just a night owl (would stay up till 11 or midnight, then sleep 9 hours). I had to just gradually adjust his clock until he was going to bed earlier and getting up in time. I still have to wake him up some mornings, but it's much better. He has adjusted beautifully.
Before preschool, it didn't really matter. He was getting enough sleep, so I let him stay up and sleep in.
I have to keep in mind that he will probably always be a night owl if I let him, so it's up to me to make sure he gets to bed on time.