24 Sekki

24 Sekki is a traditional way of expressing seasons in Japan and is defined by the ecliptic longitude of the Sun. 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 Sekki was 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.

[24 Sekki]
Season Sekki Month Longitude Meaning
Spring Risshun 1st Setsu 315° Coldest days are almost over and we can feel the sign of spring.
Usui 1st Chuu 330° It becomes warmer. Snow and ice starts melting and snow becomes rain.
Keichitsu 2nd Setsu 345° Insects come out of hibernation.
Shunbun 2nd Chuu Length of day and night becomes nearly equal.
Seimei 3rd Setsu 15° Everything looks fresh and pure.
Kokuu 3rd Chuu 30° Spring rain showers for grains.
Summer Rikka 4th Setsu 45° We feel the sign of Summer.
Shouman 4th Chuu 60° Everything grows.
Boushu 5th Setsu 75° Time to plant grains
Geshi 5th Chuu 90° Length of day becomes longest.
Shousho 6th Setsu 105° Times when the rainy season ends and it becomes hot
Taisho 6th Chuu 120° Hottest days
Fall Risshuu 7th Setsu 135° Times when we feel the sign of fall
Shosho 7th Chuu 150° Times when we feel less heat
Hakuro 8th Setsu 165° White dew stays on the grass.
Shuubun 8th Chuu 180° Length of day and night becomes nearly equal.
Kanro 9th Setsu 195° Cold dews drops on wild grasses.
Soukou 9th Chuu 210° Times when frost falls
Winter Rittou 10th Setsu 225° Times when we feel the sign of winter
Shousetsu 10th Chuu 240° Chilly Season. Rain becomes Snow.
Taisetsu 11th Setsu 255° Snow starts falling
Touji 11th Chuu 270° Times when the length of a day becomes shortest
Shoukan 12th Setsu 285° Start of cold season
Daikan 12th Chuu 300° Coldest days


Zassetsu is another sign of season that complements 24 Sekki. Doyou and Higan shows the start day of Doyou and Higan period, respectively.

Name Longitude Explanation
Doyou 27°, 117°,
207°, 297°
In the old days, Doyou is the 18 day period before Risshun, Rikka, Risshuu, and Rittou.
Setsubun - The border of seasons. Originally we had 4 Setsubun for each season, but we only refer the spring Setsubun nowadays. The next day of Setsubun is Risshun.
Higan - Higan is the 7 day period from 3 days before Shunbun (or Shuubun) to 3 days after Shunbun (or Shuubun). 1st day of Higan is called "Higan no Iri", and the last day of Higan is called "Ake".
88 Ya - The 88th day from Risshun. Times when frost is fewer.
Nyuubai 80° In the old days, Mizunoe after Boushu. Times when rainy season comes.
Hangeshou 100° In the old days, it was the 10th day from Geshi.
210 Ka - The 210th day from Risshun.