How did 18 emerge as the standard age of adulthood in most of . . . - Reddit Military service was however 18 By the turn of the century, due to labor laws, and arbitrary laws concerning alcohol consumption etc, 18 was generally seen as the age of "Adulthood " this gets muddied by age of consent laws which differs country to country and culture to culture i e it's 14 in Italy and and 16 in a lot of other countries