What is the normal bedtime for an 18 month old?

It could be possible that it is due to teething, babies are different, BUT He is 18 months. Unless he knows how to tell time, then he can't respect that you want himto sleep in until 6AM. Moving his bed time a hour back may help, but you won't knoiw until you try. If this method doesn't work or unless you teach him to tell time, then you will just have to deal with it. Kids are your priority and your Alarm Clock at times unfortunately. Good Luck