How to Use the Korean Seasonal Festival Dates Calculator
Daeboreum and Dongji are two of Korea's best-known traditional seasonal days. Daeboreum, meaning "great full moon," falls on the 15th day of the 1st lunar month — the first full moon of the lunar year. Dongji is one of the 24 traditional East Asian solar terms and marks the day the sun sits lowest in the sky, giving the year's longest night; it's also simply the astronomical winter solstice, an event every culture observes in some form. Because both dates shift slightly on the Gregorian calendar each year, select a year above and this calculator works out both dates for you.
Daeboreum is calculated as exactly 14 days after Seollal (Lunar New Year, the 1st day of the 1st lunar month), so this tool simply adds 14 days to that year's Seollal date. Dongji is computed astronomically, from the sun's position (ecliptic longitude 270°), and because Earth's orbit isn't a perfectly round 365 days, it lands on either December 21 or 22 depending on the year.
On Daeboreum, it's traditional to crack nuts like peanuts or walnuts between your teeth — a custom believed to ward off skin boils for the year — and to eat five-grain rice with seasoned vegetables for good health and a bountiful harvest. On Dongji, many Koreans eat red bean porridge (patjuk), traditionally believed to drive away bad luck. Neither custom has a scientific basis; both are simply long-running pieces of Korean folk culture worth knowing about, similar to how many countries mark the winter solstice with their own traditions.
Frequently Asked Questions
Daeboreum falls on the 15th day of the 1st lunar month — exactly 14 days after Seollal (Lunar New Year, the 1st day of that same month). Since both dates sit within the same lunar month, adding 14 days to Seollal's Gregorian date gives the exact result.
Dongji marks the astronomical moment the sun reaches its southernmost point (the winter solstice). Because Earth's orbit isn't exactly 365 days, that moment drifts slightly, landing on December 21 or 22 depending on the year.