Haji (Kor. 하지, Chin. 夏至, lit. summer reach) is the tenth of the twenty-four solar terms. It occurs between Mangjong (Kor. 망종, Chin. 芒種, Bearded Grain) and Soseo (Kor. 소서, Chin. 小暑, Minor Heat) and is some time in the fifth lunar month. On the Gregorian calendar, Haji falls around June twenty-second. The sun appears at its northernmost point (referred to as hajijeom (Kor. 하지점, Chin. 夏至點, summer solstice point)) on the ecliptic and its declination is greatest on this day.
The meridian altitude of the sun at the summer solstice reaches 75° 57′ in Seoul (37° 30′ north latitude); the sun reaches the highest point at noon, and the earth receives the largest amount of solar radiation. The summer solstice is also the longest day and shortest night of the year.
Farmers prepare for potential floods during the monsoon season, droughts, and invasions of pests around this time. They also sow buckwheat seeds, breed silkworms, harvest potatoes, garlic, barley, and hemp, plant rice, and weed chili fields. If the summer rains have not started until Haji, farmers performed a series of sacrificial rites known as giuje (Kor. 기우제, Chin. 祈雨祭, lit. ritual praying for the rain).