DS1 was 3 years 7 months before I one day just decided to put him in undies and send him to CC as was over the nappies! He did very well and no issues and had 2 accidents only in 2 weeks and both were when got distracted on way to toilet, poo's took a week. Night TT he told us on his 4th birthday was not wearing a nappy to bed as he was a big boy!

DS2 was 3 years 1 month and was relativly easy just needed push at start to go. However poo's in toilet took him till 4 years 5 months before he would not do in a nappy! He would put on a nappy do a poo and bring us wipes and a bag to change him!! (would hold on allday if we were out or at CC) No matter what sort of bribes we tried nothing was working, so we stopped saying anything about it and in the end he told me 1 day he had done a poo at CC, ad next day I said hay go to a poo in toilet and he did!! End off issue.
He is no where near night trained as often wet in morning but night time is a developmental shift and can take till age of 7 for night.

Good luck it will happen.