So pretty much all Americans know that the first two (and arguably most significant in adulthood) adulthood milestone birthdays are 18 and 21 due to the legal rights/abilities gained at each of those ages. But that leaves two birthdays in the middle of those two significant birthdays, which are 19 and 20. So between those two birthdays, which would you say is more of a milestone or closer to being a milestone birthday and why?