I know this is a regular subject but I have a slightly different twist on it! Three and a half year old has recently taken to waking early: anytime between 3.45 and 5.00. He used to never wake before 6.30 - 7.00.
The thing that seems to be causing it is that he has become a bit afraid of the dark. So, unlike others whose problem is solved by blackout curtains mine has the opposite! He has a night light but as soon as I put him to bed and close his door he switches on his main light. Throughout the night if I am up I will slip in and quietly switch his light off, but he switches it on as soon as he wakes or uses his potty. I am sure this is keeping him awake once he wakes at 3,4,5 etc.
He will play in his room (loudly!) after waking but obviously has no idea when is "getting up time" so regularly shouts "is it waking up time?"! This, and his noisy play, is what wakes me via the monitor.
He goes to bed at 7. I tried pushing it to 7.30 but it made no difference. He stopped daytime naps about a year ago.
What I would do for a lie-in..... :(