Sexagenary cycle

Sexegenary cycle

Japanese: 干支 Kan-shi or E-to

From ancient times China had two series of characters used for numbering (not for numbers!). One is the "ten stems" （jik-kan 十干), the other is the "twelve branches" (jûni-shi 十二支). They were combined to make a cycle of 60, the sexegenary cycle.These series spread over east and south-east Asia and were taken over by the Japanese from very early. They are still known in Japan, though since the Meiji period (1868-1912) their use has been very limited.

TheTwelve Branches (Jûni-shi 十二支)

general

The shi characters, translated variously as "branches," "zodiacal characters," "horary characters," etc. are a series of twelve characters used for various "cyclic" purposes. They were used for indicating direction, time, and, together with the kan, for indicating years and days. Often, though, days and years are referred to by the shi element only, without the kan. The shi early on became associated with animals, but the characters for the shi and the animals are completely distinct.

The Ten stems (Jik-kan 十干)

General

The ten kan characters are the yang (陽) and yin (陰) of the five elements of wood, fire, earch, metal, and water. They were particularly used together with the shi in the sexedecimal cycle. Kô through bo were also sometimes used to designate the night hours from inu to tora. However, now in Japan their use is mainly limited to indicating rankings, as for academic grades, or for distinguishing parties in a contract (such as, "Kô agrees to pay to otsu or an agent that otsu selects..."). In these uses, the Chinese readings are used. The kan are thus not as cyclical as the shi are.

The sexagesimal (60-character) cycle

general

When the two cycles are used together, one gets a series of sixty pairs of characters as in the table below. (60 is the least common multiple of 10 and 12.) Note that each shi is used only with either the "elder brother" ("upper") kan or with the "youger brother" ("lower") kan: odd-numbered shi go with odd-number, or upper, kan, and even-numbered shi go with even-numbered, or lower, kan. This means, for example, that a translation of tsuchinoe-tatsu as "Earth-Dragon" instead of "Elder Brother of Earth-Dragon" is unambiguous.

These pairs are normally read using the Japanese readings, as kinoe-ne for 甲子.

From the numbers of a given K(an) and S(hi) the P(osition) in the cycle can be computed as follows: if K>=S: P = (K-S)*10+K; if S>K: P = (12+K-S)*10+K. So kanoto-u (8,4) is the 28th position, and hinoe-tatsu (3,5) is in the 53rd. One can also search in the table below.

The cycle was used to indicate days, and especially year dates. For example, 1504 was a kinoe-ne year. Dating documents by cyclic years was very common, but dating documents by cyclic days was extremely rare in Japan from what I have seen. However, as the cycle repeats every 60 years (or days), the cyclic indication is not enough to determine a date; one has to have some other information. To find the year associated with a kan-shi, use the table below and add or subtract a multiple of sixty as needed, or use the method in the year dates article.

As mentioned above, when used as a date, the Japanese reading is used for the kan-shi. However when a kan-shi is used as part of a proper name, the Chinese reading are used. Thus, the Boshin War (戊辰戦争) took place in 1868, a tsuchinoe-tatsu 戊辰 year, and all high school baseball players dream of playing in Kôshien Stadium (甲子園), which opened the kinoe-ne 甲子 year of 1924.