How Is Age Calculated?
Age in most countries is calculated as the number of complete years since birth — a birthday is celebrated when the full year anniversary arrives. In this system, someone born on June 15, 2000 turns 24 years old on June 15, 2024, even if today is June 14, 2024 (the day before they're technically 24).
Exact age includes years, months, and days: a person born March 10, 1990 on November 15, 2024 is 34 years, 8 months, and 5 days old.
Interestingly, age calculation varies culturally. In traditional East Asian age-reckoning (Korea, China, Vietnam), everyone is considered 1 year old at birth (counting the year in the womb) and gains a year on January 1 of each year rather than on their birthday. A baby born on December 31 is '1 year old' for one day, then '2 years old' on January 1. South Korea officially abolished this system in June 2023, standardizing to the international method.