Earthly Branches


The twelve Earthly Branches or Terrestrial Branches are a Chinese ordering system used throughout East Asia in various contexts, including its ancient dating system, astrological traditions, zodiac and ordinals.

Origin

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 歲星 Suìxīng. Astronomers rounded the orbit of Suixing to 12 years. Suixing was associated with 攝提 Shètí and sometimes called Sheti.

History

In correlative thinking, the 12 years of the Jupiter cycle also identify the 12 months of the year, 12 animals, directions, seasons, 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, 午時 wǔshí means noon or a period from 11 am to 1 pm.
Chinese seasons are based on observations of the sun and stars. Many Chinese calendrical systems have started the new year on the second new moon after the winter solstice.
The Earthly Branches are today used with the Heavenly Stems in the current version of the "traditional Chinese calendar" and in Taoism. The Ganzhi combination is a fairly new way to mark time; in the second millennium BC, during the Shang era, the 10 Heavenly Stems provided the names of the days of the week. The Branches are as old as the Stems, but the Stems were tied to the ritual calendars of Chinese kings.

Twelve branches

Some cultures assign different animals: Vietnam replaces the Ox and Rabbit with the water buffalo and cat, respectively; Tibet replaces the Rooster with the bird. In the traditional Kazakh version of the 12 year animal cycle, the Dragon is substituted by a snail, and the Tiger appears as a leopard.

Directions

Though Chinese has words for the four cardinal directions, Chinese mariners and astronomers/astrologers preferred using the 12 directions of the Earthly Branches, which is somewhat similar to the modern-day practice of English-speaking pilots using o'clock for directions. Since 12 points were not enough for sailing, 12 midpoints were added. Instead of combining two adjacent direction names, they assigned new names:
The 24 directions are:
CharacterMandarin nameCantonese nameHokkien nameKorean nameJapanese nameRyukyuan Vietnamese nameDirection
1子ㄗˇ zǐzi2chú자 ね にー tí 0°
2癸ㄍㄨㄟˇ guǐgwai3kúi계 みずのと みんぬとぅ quý15°
3丑ㄔㄡˇ chǒucau2thiú축 うし うし sửu30°
4艮ㄍㄣˋ gèngan3kùn간 うしとら うしとぅら cấn45°
5寅ㄧㄣˊ yínjan4în인 とら とぅら dần60°
6甲ㄐㄧㄚˇ jiǎgaap3kap / kah갑 きのえ ちにー giáp75°
7卯ㄇㄠˇ mǎomaau5báu묘 う う mão 90°
8乙ㄧˇ yǐjyut3it을 きのと ちぬとぅất105°
9辰ㄔㄣˊ chénsan4sîn진 たつ たち thìn 120°
10巽ㄒㄩㄣˋ xùnseon3sùn손 たつみ たちみー tốn135°
11巳ㄙˋ sìzi6sū사 み みー tị150°
12丙ㄅㄧㄥˇ bǐngbing2péng병 ひのえ ふぃにー bính165°
13午ㄨˇ wǔng5ngó͘오 うま うま ngọ180ㄑ°
14丁ㄉㄧㄥ dīngding1teng정 ひのと ふぃぬとぅ đinh195°
15未ㄨㄟˋ wèimei6bī미 ひつじ ふぃちじ mùi 210°
16坤ㄎㄨㄣ kūnkwan1khun곤 ひつじさる ふぃちじさーるー khôn225°
17申ㄕㄣ shēnsan1sin신 さる さーるー thân240°
18庚ㄍㄥ gēnggang1keng경 かのえ かにー canh255°
19酉ㄧㄡˇ yǒuyau5iú유 とり とぅい dậu270°
20辛ㄒㄧㄣ xīnsan1sin신 かのと かぬとぅ tân285°
21戌ㄒㄩ xūseotsut술 いぬ いん tuất300°
22乾ㄑㄧㄢˊ qiánkin4khiân건 いぬい いんいー càn 315°
23亥ㄏㄞˋ hàihoi6hāi해 い いー hợi330°
24壬ㄖㄣˊ rénjam4jîm임 みずのえ みんにい nhâm345°

Advanced mariners such as Zheng He used 48-point compasses. An additional midpoint was called by a combination of its two closest basic directions, such as 丙午 for the direction of 172.5°, the midpoint between 丙, 165°, and 午, 180°.

Current usage

The terrestrial branches are still commonly used nowadays in Chinese counting systems similar to the way the alphabet is used in English. For example, names in legal documents and contracts where English speakers would use K, L, M, etc. Korea and Japan also use terrestrial branches on legal documents in this way.
Since the celestial stems and terrestrial branches combined only consist of 22 characters, the four final letters – W, X, Y, and Z – cannot be represented by any of the celestial stems and terrestrial branches, and those four letters are represented by ‘物’, ‘天’, ‘地’, and ‘人’, respectively, instead.
In case of upper-case letters, the radical of ‘口’ may be added to the corresponding terrestrial branch or any of ‘物’, ‘天’, ‘地’, and ‘人’ to denote an upper-case letter.