Sexagenary cycle

The sexagenary cycle  is a cyclic numeral system of  combinations of the two basic cycles, the   (天干; tiāngān) and the   (地支; dìzhī). These have been traditionally used as a means of numbering days and years, not only in China but also in other n nations like, , and. It is also an important part of.

Overview
The cycle was used in China since the second millennium BC (it has been found on ), as a means of naming days (just as we use the days in the week). This use of the cycle for days is attested throughout the. For instance, most entries in the use this system.

Its use for recording years is more recent. It became widespread in the (202 BC- 8 AD), and might have began in the late. According to , the calendar was transmitted to Japan in 553. But it was not until the era around 602 that the calendar was used for politics.

The calendar is calculated by combining the jikkan (十干) and jūnishi (十二支). These two sets of terms were used to enumerate years of the civil calendar. Combining the series form a greater cycle of 60 terms, as the of 10 and 12 is 60. The first term is formed by adding the first stem to the first branch, then the second stem to the second branch, and so on. If you start with kinoe-ne/kōshi (甲子), so the 61st year would also be kinoe-ne. This was how the tradition of celebrating the 60th birthday (還暦) began. This counting system employing things of nature and animals create many myths, and people of Japan today still consider the good and bad luck of certain days and years.

The year 604, when the Japanese officially adopted the Chinese calendar, was the first year of the cycle. The year 1984 began the present cycle, and 2044 will begin another.

Twelve Earthly Branches
* The names of several animals can be translated into English in several different ways. The Vietnamese Earthly Branches use instead of Rabbit/Hare.

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 rat but not the cat. 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.

Sexagenary Cycle
The sexagenary cycle was first used for days in the, and later also used for years and less commonly for months.

For example, the year 2000 was 17th year of the 78th sexagenary cycle, a gēng-chén year (庚辰年), a year of the Yang Metal Dragon. Therefore, is 23rd year of the 78th sexagenary cycle, called a bǐng-xū year (丙戌年), a year of the Yang Fire Dog;  a year of the Yin Fire Pig.

The naming of the months and days is not common now, although they are shown on Chinese calendars and almanacs.

Relation to western calendar
Below is the sexagenary cycle matched up to the Western calendar for the years 1804 - 2043, or four full 60 year cycles.