How age is calculated
Age in years counts the birthdays that have passed: subtract the birth year from the current year, then take one away if this year's birthday has not happened yet. Months and days are counted from the most recent birthday.
Born on February 29?
In non-leap years, the birthday countdown uses March 1. Many countries treat March 1 as the legal birthday in those years, though some use February 28.
Korean age
Korea traditionally counted everyone as one year old at birth and added a year every January 1. Since June 2023, Korean law uses international age, the same as this calculator.