The Earthly Branches (Chinese: 地支; pinyin: dìzhī; or 十二支, shíèrzhī, "twelve branches") is an ancient Chinese cyclic numeral system once used to count days and years but now used only in conjunction with the Heavenly Stems in the traditional calendar and Taoism. There are twelve phonetic characters in the system, each corresponding to an animal of the Chinese zodiac, and a respective direction, season, month, and Chinese hour (a modern double hour). The association to twelve animals is still common throughout East Asia.

The seasons are based on the movement of the sun, not the weather. A Chinese new year usually starts on the new moon day closest to the midpoint between the winter solstice and the vernal equinox.

When a Branch is used for the exact time of a day, the listed hours are used. When used for a period, it means a period from one hour before to one hour after. For instance, 午 (the Horse) means noon or a period from 11am to 1pm.

Some cultures assign different animals: the second animal is the water buffalo in Vietnam, the fourth is the cat in Vietnam and Thailand, and the twelfth is the wild boar in Japan.

Some researchers think the origin of the Earthly Branches may be foreign, because twelve differs from the Chinese culture's preference for the decimal system. The Heavenly stems, which are clearly decimal, appeared hundreds of years before the first use of the Earthly Branches. The association to twelve animals was a later invention, probably affected by the Mesopotamian zodiac imported through India and Tibet. This is why the Chinese zodiac has no relation to Chinese constellations.

Directions

Even though Chinese has words for the four cardinal directions - 北 (běi, north), 東 (dōng, east), 南 (nán, south), and 西 (xī, west) - Chinese mariners and astronomers preferred using the twelve directions of the Earthly Branches, which is somewhat similar to using o'clock for directions. Since twelve points were not enough especially for sailing, twelve midpoints were added later. 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 甲 (jiǎ) and 乙 (yǐ). Thus they were assigned clockwise to the two adjacent points of the east.

Here is a table of the 24 directions.

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 丙午 (bǐngwǔ) for the direction of 172.5°, the midpoint between 丙 (bǐng), 165°, and 午 (wǔ), 180°.

See also

• Sexagesimal cycle (干支)
• Chinese calendar

External links

• Heavenly Stems and Earthly Branches - Hong Kong Observatory