My son, now 15 months old, was sleeping through the night, and waking up consistently at 6am. However, over the past few months he had been gradually waking up earlier. Now he wakes up consistently at 5am. For a while I was able to go in and say "it is still too early; go back to sleep" and he would lie back down and fall asleep for another half hour - 45 minutes. However, that no longer works, and he won't go back to sleep until after he's had a bottle of milk.
The other night he was woken up accidentally around 11pm (he normally goes to sleep around 8:30pm). We gave him a small bottle of milk, and then put him back to bed. The next morning he still woke up at 5am, so I do not think it is an issue of him being awakened by hunger.
How can we help shift his wake up time back to 6am-6:30am? Waking up at 5am each morning is getting to be a real strain on our schedules.