3 year old waking up at 5am every day

Ever since my son dropped his nap he’s been waking up at 5 am. We tried ok to wake clocks and keeping him in his dark room until 6 but it hasn’t worked. We’ve tried putting him down at 6pm to prevent him being overtired but he sleeps from 6pm-5am every night.

Has anyone gone through this or figured out how to solve it? I know all about this for baby sleep and how putting down later makes them wake earlier, but I’m wondering if since he’s 3 now it would help him wake up later if he went to bed later