Korean calendar (traditional lunisolar calendar)

Structure and key features

The calendar measures months by lunar cycles: each month begins with a new moon and lasts about 29–30 days. To prevent the lunar year from drifting away from the solar seasons, one extra month (an intercalary or leap month) is inserted in some years. Years are often identified using the traditional sexagenary cycle of stems and branches, a pattern shared across the region. This combination of lunar months and periodic leap months makes the calendar lunisolar.

Major festivals and observances

Many of Korea’s best-known traditional holidays still follow this calendar rather than the Gregorian calendar. Important examples include:

• Seollal — the Lunar New Year, typically celebrated in late January or February; it is the most widely observed traditional holiday and a principal family festival.
• Daeboreum — the first full moon of the new lunar year, often called Boreumdal; associated with customs intended to ensure good fortune for the year.
• Chuseok — an autumnal harvest festival, observed around the full moon in the eighth lunar month; a time for family reunions and ancestral rites.
• Dano — a spring festival on the fifth day of the fifth lunar month, linked to seasonal rites and traditional games.
• Samjinnal and other seasonal markers — Samjinnal (the third day of the third lunar month) celebrates the beginning of spring; other dates such as Yudu and Chilseok mark midsummer and monsoon-related seasonal points.

History and development

The Korean calendrical tradition was strongly influenced by Chinese astronomical and calendrical systems, and local Korean adjustments were made over centuries. During the late 19th century reforms and the modernization of government institutions, Korea adopted the Gregorian calendar for civil use; the Gregorian system officially replaced the traditional calendar for most administrative and everyday dating purposes in the 1890s. Despite that change, the lunisolar calendar continued to be used for cultural, religious and agricultural scheduling.

Modern use and cultural importance

Today, the Gregorian calendar is used for official business and daily life in Korea, but the traditional lunisolar calendar remains central to cultural identity. Families consult it for festival dates, ancestral memorials, and some folk rituals. Agricultural communities and certain religious groups may still reference the lunisolar calendar for timing seasonal activities. General information on East Asian calendrical traditions and comparative practices can be found in broader sources about regional calendars: East Asian calendars and the Chinese-origin systems summarized at Chinese calendar. For the modern civil transition, see references on the adoption of the Gregorian calendar and for specifics about lunar festivals such as Daeboreum consult resources on traditional holidays: Daeboreum and related observances.