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KEMI Tools

Age, D-day & Date Calculator

Get international (man) age, year age, zodiac and days to your next birthday from a birth date — then switch tabs for D-day, 100/1000-day anniversaries, date add/subtract, days between dates, and business days excluding weekends and 2026 Korean holidays. Pure calendar-date math, no timezone drift, nothing leaves your browser.

Loading today’s date…

How to use

  1. Pick a birth date on the Age tab; change ‘As of’ to see the age on a specific date.
  2. On D-day, enter a target for the countdown or a start date for the anniversary table.
  3. Date math adds or subtracts days/weeks/months and measures spans between dates.
  4. Business days counts weekdays minus 2026 holidays, or finds the date N business days later.

Law

Korea’s unified ‘man’ age (since 28 June 2023)

Korea used to mix three ages: counting age (1 at birth, +1 every New Year), year age, and international age. Since June 2023, the Civil Act Art. 158 and the Framework Act on Public Administration Art. 7-2 make international age the default in laws, contracts and documents. Exceptions remain — the Juvenile Protection Act still lets people buy alcohol from 1 January of the year they turn 19.

Born 2000-10-05, as of 2026-10-04:
  2026 − 2000 = 26, birthday not reached yet → man age 25
Anniversary: start 2026-01-01 = day 1 → day 100 = 2026-04-10 (start + 99)

Common pitfalls: confusing inclusive and exclusive day counts, month-end clamping (31 Jan + 1 month = 28 Feb), and timezone/DST errors when subtracting local-midnight timestamps. This tool works on pure calendar dates. Business days use the full 2026 holiday list, including substitute holidays and the 3 June local election — 245 weekdays in 2026.

FAQ

Which age is official in Korea now?

Since 28 June 2023 the Framework Act on Public Administration (Art. 7-2) and the Civil Act (Art. 158) use international ‘man’ age unless another law says otherwise. Alcohol and tobacco rules still use year age (from 1 January of the year you turn 19).

How are 100-day anniversaries counted?

Korean custom counts the start day as day 1, so day 100 is the start date plus 99 days (1 Jan 2026 → 10 Apr 2026).

Is today included in D-day?

No. D-n is the number of days remaining, excluding today and including the target day.

Which holidays are excluded from business days?

All 2026 Korean public holidays, including substitute holidays, the 3 June local election, and Labor Day and Constitution Day (holidays from 2026). Company-specific days off are not included.

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