Suddenly waking up early?!

My son is 3.5yo, he used to sleep from 8pm to about 8am, sometimes 7:30 but no earlier.

Now all of a sudden 6:30am on the dot he is up and ready to go! Literally nothing has changed, if anything we may be outside & playing MORE now that the weather is nicer! By the time dinner comes around he is exhausted. Not to mention I’m up with my youngest quite a bit through the night still, that extra little bit of sleep helps so much.

He has blackout curtains, I even have a blanket over the top to stop the sun coming in, (this was before he even started waking up). He also sleeps with a white noise machine.

Anyone have any idea why there would be a sudden change in his routine? it literally started on Monday out of the blue & has been going on all week.