The Earthly Branches ( ; or ) 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 Suìxīng (Jupiter, the Year Star). Astronomers rounded the orbit of Suixing to 12 years (from 11.86). Suixing was associated with Sheti (ɳ Boötes) 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. Many Chinese calendrical systems have started the new year on the first new moon after the winter solstice.

The Earthly Branches are today used with the Heavenly Stems in the current version of the "traditional calendar" and in Taoism. The Ganzhi (Stem-Branch) combination is a fairly new way to mark time; in the Shang era it was the ten Heavenly Stems that provided the names of the days of the week. The Branches are as old as the Stems (and according to recent archaeology may actually be older), but the Stems were tied to the ritual calendars of Chinese kings. They were not part of the calendrical systems of the majority of Chinese.

	Earthly Branch	Chinese name	Japanese name		Korean name	Vietnamese name	Chinese zodiac	Direction	Season	Lunar Month	Double Hour
			On	Kun
1	子	zǐ	shi	ne	자 (ja)	tý (Tí)	Rat	0°(north)	winter	Month 11	11pm to 1am (midnight)
2	丑	chǒu	chū	ushi	축 (chuk)	sửu	Ox	30°		Month 12	1am to 3am
3	寅	yín	in	tora	인 (in)	dần	Tiger	60°	spring	Month 1	3am to 5am
4	卯	mǎo	bō	u	묘 (myo)	mão (mẹo)	Rabbit	90° (east)		Month 2	5am to 7am
5	辰	chén	shin	tatsu	진 (jin)	thìn	Dragon	120°		Month 3	7am to 9 am
6	巳	sì	shi	mi	사 (sa)	tỵ	Snake	150°	summer	Month 4	9am to 11am
7	午	wǔ	go	uma	오 (o)	ngọ	Horse	180° (south)		Month 5	11am to 1pm (noon)
8	未	wèi	bi	hitsuji	미 (mi)	mùi	Sheep	210°		Month 6	1pm to 3pm
9	申	shēn	shin	saru	신 (sin)	thân	Monkey	240°	autumn	Month 7	3pm to 5pm
10	酉	yǒu	yū	tori	유 (yu)	dậu	Rooster	270° (west)		Month 8	5pm to 7pm
11	戌	xū	jutsu	inu	술 (sul)	tuất	Dog	300°		Month 9	7pm to 9pm
12	亥	hài	gai	i	해 (hae)	hợi	Pig	330°	winter	Month 10	9pm to 11pm

Some cultures assign different animals: Vietnam replaces the ox, rabbit, and sheep with the water buffalo, cat, and goat respectively; Japan replaces the pig with the wild boar. In the traditional Kazakh version of the 12-year animal cycle ( , müşel), the dragon is substituted by a snail ( , ulw), and the tiger appears as a leopard ( , barıs).

Directions

Even though Chinese has words for the four cardinal directions - (běi, north), (dōng, east), (nán, south), and (xī, west) - Chinese mariners and astronomers/astrologers preferred using the twelve directions of the Earthly Branches, which is somewhat similar to the modern-day practice of English-speaking pilots using o'clock for directions. Since twelve points were not enough for sailing, twelve midpoints were added. Instead of combining two adjacent direction names, they assigned new names as follows:

• For the four diagonal directions, appropriate trigram names of I Ching were used.
• For the rest, the Heavenly Stems were used. According to the Five Elements theory, east is assigned to wood, and the Stems of wood are (jiǎ) and (yǐ). Thus they were assigned clockwise to the two adjacent points of the east.

Following is a table of the 24 directions:

	Character	Chinese name	Japanese name	Direction
1	子	zǐ	ne	0° (north)
2	癸	guǐ	mizunoto	15°
3	丑	chǒu	ushi	30°
4	艮	gèn	ushitora	45° (northeast)
5	寅	yín	tora	60°
6	甲	jiǎ	kinoe	75°
7	卯	mǎo	u	90° (east)
8	乙	yǐ	kinoto	105°
9	辰	chén	tatsu	120°
10	巽	xùn	tatsumi	135° (southeast)
11	巳	sì	mi	150°
12	丙	bǐng	hinoe	165°
13	午	wǔ	uma	180° (south)
14	丁	dīng	hinoto	195°
15	未	wèi	hitsuji	210°
16	坤	kūn	hitsujisaru	225° (southwest)
17	申	shēn	saru	240°
18	庚	gēng	kanoe	255°
19	酉	yǒu	tori	270° (west)
20	辛	xīn	kanoto	285°
21	戌	xū	inu	300°
22	乾	qián	inui	315° (northwest)
23	亥	hài	i	330°
24	壬	rén	mizunoe	345°

Advanced mariners such as Zhèng Hé used 48-point compasses. An additional midpoint was called by a combination of its two closest basic directions, such as (bǐngwǔ) for the direction of 172.5°, the midpoint between (bǐng), 165°, and (wǔ), 180°.

See also

• Sexagesimal cycle (干支)
• Sheng Xiao
• Chinese calendar
• (A study of the cardinal directions chart)

External links

• Heavenly Stems and Earthly Branches - Hong Kong Observatory