grown up

so when exactly do you become a grown up is it the day you turn 16 or the day you turn 18 or is it when you graduate high school maybe when you have your first child or is it when you get married or is it the day you start college or is it when you start you start your first job. I dont know exactly when it happens. I know I dont feel like a grown up but everyone says I am I have done most of these things. Hmm I just know Im 20 almost 21 years old and still am a kid at heart, but I do act like an adult sometimes lol.