When did your toddler drop their naps?

My oldest is coming up on 3.5 yo and is struggling with going to sleep at both his nap and bedtime. For a long time, he would wake up around 6am and go to sleep around 1pm for his nap (long wake window, for sure), then he'd be ready for bed around 8-8:15pm without issue. Lately he's been fighting both nap time and bed time, taking an hour to fall asleep.

When did you all drop this final nap? Any recommendations on modifying current schedule? We've been trying to move his nap earlier in the day but haven't really had success. Thank you in advance!