If you do something bad when you are 17.9 should we wipe the slate clean once the odometer rolls over to exactly 18.0 where for some reason that age creates a solid barrier where the person emerges like a chrysalis and all their sins are washed clean?

And as a 50 year old, the difference between a 16 year old and a 19 year old are not very big. An unfortunate fact is that if you fuck up pretty big when you're 16 that people aren't going to trust you very much when you're 19. You need to do the time to build up more collateral. I've seen people who were assholes when they were teenagers change, but they didn't wake up on some magic birthday a new person. They were still assholes in their early 20s but their trajectory was such that by the time their early 30s came around they had changed themselves.