Korea Business Day & Public Holiday Calculator

South Korean public-holiday lookup and business-day counting for AI agents and automations. A business day here means Monday to Friday (optionally Saturday) that is not a public holiday of Korean government offices.

When to use this

Use it when a task needs the Korean public-holiday calendar: counting working days between two dates, finding the date N working days ahead, scheduling around Seollal and Chuseok, or checking whether a date is a public holiday in South Korea. Banks, stock exchanges, couriers and individual companies can have their own closing days; this tool does not know them.

Why not let the model work it out

Korean public holidays changed in 2026. Labour Day (1 May) and Constitution Day (17 July) became public holidays, substitute holidays now apply to more days, and lunar holidays move every year. In 2027 Seollal itself is Sunday 7 February, the holiday period starts on 6 February, and the substitute holiday is Tuesday 9 February. A model trained before the 2026 change can count the wrong number of days. This tool carries a table checked against the sources below and does the counting deterministically.

What it returns

Operation	Input	Output
checkDate	date	weekday, isPublicHoliday (Sundays included), isDesignatedHoliday (national days, Seollal, Chuseok, substitute, temporary and election holidays), holiday name in Korean and English, isBusinessDay
listHolidays	from, to	every designated holiday in the range (ordinary Sundays are not listed), with weekday and whether it falls on a weekend
addBusinessDays	from, days	the date N business days after (or before) from, and the designated holidays skipped
countBusinessDays	from, to	calendarDays, businessDays, designatedHolidays, otherNonWorkingDays (these three add up to calendarDays), plus saturdays and sundays

Successful results and handled errors (bad input, out-of-coverage dates, spending limit reached) carry dataVersion, coverage and sources.

Example input:

{ "operation": "addBusinessDays", "from": "2026-09-23", "days": 1 }

Example output (shortened):

{ "ok": true, "result": "2026-09-28", "resultWeekdayEn": "Mon",
  "designatedHolidaysSkipped": [
    { "date": "2026-09-24", "nameEn": "Chuseok holiday" },
    { "date": "2026-09-25", "nameEn": "Chuseok" },
    { "date": "2026-09-26", "nameEn": "Chuseok holiday" } ],
  "charged": true, "dataVersion": "2026-10-10" }

Limits

• Verified dates: 2025-01-01 to 2027-12-31. Outside this range the tool returns OUT_OF_COVERAGE and no result. It never guesses.
• Temporary holidays and election days announced after dataVersion are not included until the table is updated.
• Public (government office) holidays only. Company-specific days off, bank-specific closing days and stock market closing days are not covered.
• The result is a calendar calculation, not legal advice on how a particular contract or statute counts days.

Pricing

Pay per event. Every run has the small standard Actor start event ($0.00005). A successful result adds one calculation event ($0.005, that is $5 per 1,000 results). Platform usage is included. Input errors and out-of-coverage dates do not trigger the calculation event. If the run budget cannot cover the event, no result is returned. The event is charged before the result is stored, so in the rare case that storage fails after charging, re-run the same input and contact the developer for a refund of that event.

Data sources

• Korea AeroSpace Administration (KASA) annual calendar notice for 2027 (월력요항), announced 2026-06-29.
• Regulations on Holidays of Government Offices (관공서의 공휴일에 관한 규정), Presidential Decree No. 36290: Labour Day in force 2026-05-01, Constitution Day in force 2026-05-11.
• Korea Astronomy and Space Science Institute calendar data for 2025-2027, used as a cross-check.

The full URLs are returned in the sources field.

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한국 공휴일·영업일 계산 도구입니다. 2026년부터 노동절과 제헌절이 공휴일이 된 것, 대체공휴일, 설·추석 연휴를 반영해 영업일을 정확히 셉니다. 확인된 기간(2025~2027년) 밖의 날짜는 추측하지 않고 오류를 돌려줍니다.