Most teams reach for a per-language library (Python, Java, Go, Rust) to convert Korean lunar dates — which means a dependency in every service that needs it. This API does the same KASI-derived conversion over plain HTTP, so any stack can call it without installing anything.
Korea's traditional calendar is lunisolar: birthdays, 설날 (Lunar New Year), 추석 (Chuseok) and many family events are tracked on the lunar calendar. Converting between a solar (Gregorian) date and the Korean lunar date — correctly handling leap months (윤달) — is the building block for calendar, fortune (사주/saju) and reminder apps.
| GET | /v1/lunar/solar-to-lunar?date=1991-05-15 |
Solar (Gregorian) date to Korean lunar date + gapja pillars. |
| GET | /v1/lunar/lunar-to-solar?date=2026-01-01&leap=false |
Korean lunar date to solar date (leap=true for a leap month / 윤달). |
curl "https://korea-calendar-api.kunstudio.workers.dev/v1/lunar/solar-to-lunar?date=1991-05-15"{
"solar": "1991-05-15",
"lunar": { "year": 1991, "month": 4, "day": 2, "leap_month": false },
"gapja": { "year": "신미년", "month": "계사월", "day": "을유일" }
}No API key is needed on the origin to try this — it is rate-limited for fair evaluation. See the OpenAPI spec for the full schema.
leap=true on lunar-to-solar to resolve a 윤달 date. The reverse endpoint returns leap_month so you never lose that bit on a round trip.Building a Korean fortune (사주/saju) app? Pair this with the KunStudio Saju API for a full four-pillars reading over REST.