The international method: The change comes after South Korea’s National Assembly passed legislation in December 2022 to unify the nation's age systems with the standardized international model. According to the Ministry of Government Legislation, the international model will be used to legally document the age of Koreans in contracts, official documents and social circumstances. About the traditional age system: In Korea’s old tradition, a person is born at 1-year-old and becomes a year older each New Year’s Day.