Eto:干支 (Chinese sexagenary cycle)

 The Earthly Branches (Chinese: 地支; pinyin: dìzhī; or Chinese: 十二支; pinyin: shíèrzhī; literally "twelve branches") provide one Chinese system for reckoning time.

 This system was built from observations of the orbit of Jupiter. Chinese astronomers divided the celestial circle into 12 sections to follow the orbit of Suixing (Jupiter, the Year Star). Astronomers rounded the orbit of Suixing to 12 years (from 11.86). Suixing was associated with Sheti (ɳ Böotes) and sometimes called Sheti.

 In correlative thinking, the twelve years of the Jupiter cycle also identify the twelve months of the year, twelve animals (mnemonics for the system), directions, seasons, months, and Chinese hour in the form of double-hours. When a Branch is used for a double hour, the listed periods are meant. When used for an exact time of a day, it is the center of the period. For instance, 午 (the Horse) means noon or a period from 11am to 1pm. (The jie qi system provided single hours and 15-degree arcs in time and space.)

 Chinese seasons are based on observations of the sun and stars, not the weather. Many Chinese calendrical systems have started the new year on the first new moon after the winter solstice.

Twelve Earthly Branches

	Earthly Branch	Chinese name	Japanese name	Chinese zodiac	Corresponding hours
1	子	zǐ	shi/ne	Rat/Mouse (鼠)	11 p.m. to 1 a.m.
2	丑	chǒu	chū/ushi	Ox/Cow/Bull (牛)	1 to 3 a.m.
3	寅	yín	in/tora	Tiger (虎)	3 to 5 a.m.
4	卯	mǎo	bō/u	Rabbit (兔)	5 to 7 a.m.
5	辰	chén	shin/tatsu	Dragon (竜)	7 to 9 a.m.
6	巳	sì	shi/mi	Snake (蛇)	9 to 11 a.m.
7	午	wǔ	go/uma	Horse (馬)	11 a.m. to 1 p.m.
8	未	wèi	mi or bi/hitsuji	Sheep/Goat (羊)	1 to 3 p.m.
9	申	shēn	shin/saru	Monkey (猿)	3 to 5 p.m.
10	酉	yǒu	yū/tori	Chicken/Rooster (鶏)	5 to 7 p.m.
11	戌	xū	jutsu/inu	Dog (犬)	7 to 9 p.m.
12	亥	hài	gai/i	Pig/Boar (猪)	9 to 11 p.m.

 In a traditional story of the twelve animals, the cat and rat were once good friends, but the animals to be selected to represent the years included the cat but not the rat. These animals had to present themselves to be given the honour of representing the years in the cycle, and the cat asked the rat to wake him up before they had to go. The rat didn't do this, but instead went himself. When they came to cross a river, the rat jumped on the ox's back, and just before the ox got to the bank, the rat jumped off and was first in line. This is why the twelve animals are lead by the rat, and because the cat was cheated out of its rightful place, rats are forever sought out by cats for revenge.

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