korean_lunar_calendar

Convert between the Korean lunar calendar (음력) and the Gregorian solar calendar (양력) — entirely offline, following the KARI (Korea Astronomy and Space Science Institute) standard.

The Korean and Chinese lunar calendars share the same astronomical basis but can fall on different dates. This library uses the Korean (KARI) standard.

Features

• Two-way conversion — solar → lunar and lunar → solar.
• Offline — the conversion table is bundled; no network calls, no external services.
• GapJa (간지) strings — the sexagenary year/month/day in both Korean (정유년 병오월) and Chinese (丁酉年 丙午月).
• Leap-month aware — handles intercalation months (윤달) and the 1582 Gregorian reform gap.
• Input validation — every setter returns a bool; out-of-range, non-integer, and impossible-leap-month dates are rejected.
• Pure standard library — no third-party dependencies.

Supported range

Calendar	From	To
Lunar (음력)	1000-01-01	2050-11-18
Solar (양력)	1000-02-13	2050-12-31

Dates outside this range cause the corresponding setter to return False.

Install

pip install korean_lunar_calendar

from korean_lunar_calendar import KoreanLunarCalendar

Usage

Solar → Lunar (양력 → 음력)

calendar = KoreanLunarCalendar()

# setSolarDate(year, month, day) -> bool
calendar.setSolarDate(2017, 6, 24)

print(calendar.LunarIsoFormat())        # 2017-05-01 Intercalation
print(calendar.getGapJaString())        # 정유년 병오월 임오일 (윤월)
print(calendar.getChineseGapJaString()) # 丁酉年 丙午月 壬午日 (閏月)

Lunar → Solar (음력 → 양력)

calendar = KoreanLunarCalendar()

# setLunarDate(year, month, day, isIntercalation) -> bool
calendar.setLunarDate(1956, 1, 21, False)

print(calendar.SolarIsoFormat())  # 1956-03-03
print(calendar.getGapJaString())  # 병신년 경인월 기사일

# Intercalation (leap) month, e.g. lunar 1727-03-01 (leap) -> solar 1727-04-21
calendar.setLunarDate(1727, 3, 1, True)
print(calendar.SolarIsoFormat())  # 1727-04-21
print(calendar.getGapJaString())  # 정미년 갑진월 정사일 (윤월)

Always check the return value of setSolarDate / setLunarDate before reading the result — the accessors reflect the last successful set call.

API

KoreanLunarCalendar() creates a stateful converter. Set a date, then read it back in the other calendar.

Member	Returns	Description
setSolarDate(year, month, day)	bool	Set a Gregorian date. Returns False for out-of-range, non-integer, or nonexistent dates.
setLunarDate(year, month, day, isIntercalation)	bool	Set a lunar date. isIntercalation requests the leap month; returns False if that month has no leap month.
LunarIsoFormat()	str	Lunar date as YYYY-MM-DD, with Intercalation appended for a leap month.
SolarIsoFormat()	str	Solar date as YYYY-MM-DD.
getGapJaString()	str	Sexagenary cycle in Korean, e.g. 정유년 병오월 임오일 (윤월).
getChineseGapJaString()	str	Sexagenary cycle in Chinese characters, e.g. 丁酉年 丙午月 壬午日 (閏月).

After a successful set you can also read the components directly: lunarYear, lunarMonth, lunarDay, isIntercalation, solarYear, solarMonth, solarDay.

Validation

Every setter validates its input and returns a bool, so you can branch on the result:

calendar = KoreanLunarCalendar()

# Rejected -> returns False
calendar.setLunarDate(99, 1, 1, False)    # before supported range
calendar.setSolarDate(2051, 1, 1)         # after supported range
calendar.setSolarDate(2017, 6, 24.5)      # non-integer input
calendar.setSolarDate(1582, 10, 8)        # skipped by the 1582 Gregorian reform
calendar.setLunarDate(2017, 3, 1, True)   # month 3 of 2017 has no leap month

# Accepted -> returns True
calendar.setLunarDate(1000, 1, 1, False)
calendar.setSolarDate(2050, 12, 31)

Tests

python -m unittest -v

Other languages

• Java — usingsky/KoreanLunarCalendar
• Python — usingsky/korean_lunar_calendar_py
• JavaScript — usingsky/korean_lunar_calendar_js

Acknowledgements

Conversion data follows the KARI (Korea Astronomy and Space Science Institute) Korean lunar–solar standard. Many thanks to KARI for publishing the reference tables.

License

MIT © Jinil Lee