Birthdays : 1 (first birthday),10 (double figures), 13 (first teenage year), 16 (age of legal consent for sex and others), 18 (certain laws ...maybe smoking, drinking , driving, depending on when the government changes them and what country you are in), 21 (driving, smoking, drinking depending on government and country), 50 (half a century), 75 (three quarters of a century), 100 (a century, triple figures)