Since June 2023, age in Korean law and administration is counted the international way, as man-nai (full years). Civil Act Article 158 says age is counted including the day of birth, in full years, and expressed in years, adding that under 1 it may be expressed in months. Article 7-2 of the Framework Act on Administration applies the same rule to administration unless another law makes a special provision. Enter a birth date and a reference date to get the legal age and the days to the next birthday.
1. Legal age counts the day of birth and goes up on each birthday (Civil Act Art. 158).
2. Under 1, months may be used — “8 months”.
3. Administration uses it too, unless another law provides otherwise (Framework Act Art. 7-2).
Calculator
Updates as you type. Age counts the day of birth and goes up on the birthday. For a 29 February birthday in a non-leap year we treat the age as going up on 1 March (our reading of Civil Act Art. 160(3)).
The two articles
| Type | What the source says | Worth noting (ours) |
|---|---|---|
| Civil Act Art. 158 | Age is calculated including the day of birth, in full years, and expressed in years; under 1, it may be expressed in months. | Fully revised 27 Dec 2022 |
| Framework Act on Administration Art. 7-2 | Age in administration is calculated the same way unless another law or regulation makes a special provision; under 1, months may be used. | Added 27 Dec 2022 |
“Including the day of birth” means the birth day counts as day one. Civil Act Article 157 normally leaves out the first day when counting periods, but Article 158 puts it in for age. So age goes up on the birthday.
Three sums — our example
| Case (our example) | Legal age | Worth noting (ours) |
|---|---|---|
| Born 21 Oct 1990, as at 20 Oct 2026 | 35 | 36 the next day |
| Born 29 Feb 2000, as at 28 Feb 2026 | 25 | No 29 February in a common year |
| Same person, as at 1 Mar 2026 | 26 | Goes up on 1 March, on our reading |
| Born 10 Feb 2026, as at 20 Oct 2026 | 0 — 8 months | Under 1, months may be used |
The articles don’t deal with 29 February directly. Applying Civil Act Art. 160(3) (“if the final month has no corresponding day, the period ends on the last day of that month”), the year ends on 28 February in a common year and age goes up on 1 March. That’s our reading; check with the agency for anything important.
Why show “year minus birth year”?
Article 7-2 keeps an exception for “special provisions in other laws”. Some laws may count by birth year alone, so the calculator shows that figure for reference. We didn’t check which laws do; see each scheme’s own guidance.
When a period ends is in legal period calculator.
Checklist
- ☐ Age goes up on the birthday itself
- ☐ Under 1, months may be used
- ☐ Check each scheme for a special provision
- ☐ 29 February birthdays in common years
Questions that remain
Is the traditional Korean age gone?
The articles govern age in law and administration, not everyday talk. Contracts and forms use legal age (our note).
Does the time of birth matter?
The articles only say the day of birth is included; they don’t mention the time.
Sources
- Korean law database (law.go.kr) — Civil Act Arts. 157–160 — source (current text, effective 17 March 2026, Act No. 21454; checked 20 October 2026). Art. 158 on age (birth day included, full years, months), Art. 157 first-day rule, Art. 160(3) end-of-month.
- Korean law database — Framework Act on Administration Art. 7-2 — source (current text, effective 19 March 2026, Act No. 20824; checked 20 October 2026). Age in administration and the special-provision exception.
- Not read. Individual laws with their own age rules.
- What we added. The “worth noting” column and the Korean everyday gloss.
Where to check further
- The scheme’s own guidance — any special age rule.
Written on 20 October 2026. The content is from the source; the glosses are ours.
