About 24 Solar Terms


Winter, 10th "Setsu". when the sun reaches 225° in longitude. Beginning of Winter; Times when we feel the sign of winter.
Winter, 10th "Chuu". when the sun reaches 240° in longitude. Light Snow; Chilly Season. Rain becomes Snow.

"24 Sekki" or 24 Solar Terms are traditional ways of expressing seasons in Japan and China. Each term is defined by the ecliptic longitude of the Sun (λ). For example, "Shunbun" is the time when the longitude of the Sun becomes 0°, and "Shuubun" is when the longitude becomes 180°. In luni-solar calendar era, 24 Solar Terms were also necessary for deciding when to insert leap month. A year has four seasons, and each season has 3 "Setsu" and 3 "Chuu" arranged alternately.