Korea switched to international age for laws and contracts in June 2023, so documents often mix three different age counts. This page resolves all three and handles the surrounding date math.
Three age counts
Exact age increases on the birthday. Korean counting age increases when the calendar year changes. Year age is simply the current year minus the birth year, used in conscription and youth protection law. The same person can differ by up to two years across the three.
Inclusive or exclusive days
Hotel nights, working days and event spans usually count the first day too, so both the plain difference and the inclusive count are shown. Check which one the contract wording means.
Everything stays local
Birth dates and target dates are calculated in the current browser and never sent to a server or stored. Nothing remains once the tab is closed.
