East Asian Age Reckoning
In the traditional Korean, Chinese, and Japanese counting systems, a baby is 1 year old at birth, and everyone ages one year on New Year's Day rather than on their birthday. Under this system, a baby born on December 31 becomes 2 years old the very next day (January 1), despite being only one day old by Western counting. South Korea officially abandoned this system in June 2023, switching to the international standard for all legal and administrative purposes. The change affected medical guidelines, insurance premiums, and military service eligibility for millions.