why is my 2 year old sleeping so much less?

he used to sleep from 10pm-8am and nap for 3 hours. for the last 2 weeks he's sleeping from 1030pm- 5 or 6 am! and only napping 1 1/2 hours.

i know as they get older they need less sleep but that's a fast and dramatic change!

he cut 2 eye teeth a few weeks ago and has no new teeth coming in.