When I was 15 years old, I got very sick.
After that, I saw the world in a whole other view. I was 'mature'.
I barely had any real connection with kids of my age. To this day I still got trust issues
Fun fact: when I became 18, I felt kinda right.
I agree. A number does not define if you are an adult or mature. It are the events that ones experience in life that determined whether you feel mature.
But I am not saying that you cannot grow into an adult without any drastic event. In fact, I envy those (in a good way) who turn into a mature adult in a natural way without any drastic experiences.
I think that, mature adults are those who realize their existence in this world, who can listen to another with an unbiased view and who can respect each other for the person they are.