Chinese calendar: lunisolar system, structure, history and cultural role

The Chinese calendar is a combination of a bound lunar calendar (lunisolar calendar, i.e. a lunar calendar with leap months) and a solar calendar. There is a parallel lunar year (年, nián) and a solar year (歲 / 岁, suì). The term "peasant calendar" used to refer only to the solar calendar.

Solar calendar

The solar year sui begins on the day of the winter solstice and is - as in the Gregorian calendar - always 365 or 366 days long.

The path that the sun apparently traverses on the ecliptic within a tropical year of 365.24 days is divided into 24 parts of 15° each. These are the 24 stations or divisions of the year (節氣 / 节气, jiéqì). Every other station is a zhongqi (中氣 / 中气, zhōngqì - "central/main year division"), with the solstices and equinoxes being four of the twelve zhongqi. The time interval from one zhongqi to the next averages one twelfth of a tropical year, or 30.44 days. It varies slightly due to the elliptical orbit of the earth around the sun.

The 24 stations are traditionally important for Chinese agriculture and are still recorded in most calendars in China. Climatically, they apply more to northern China, less to southern China.

Each of the six divisions of the year belongs to one season. But while in the western calendar the seasons begin with the day of the solstice or the equinox, in the Chinese calendar these days lie in the middle of the respective season. The stations are counted starting with the beginning of spring - lichun, and in some places the beginning of spring (and not the winter solstice) is considered the beginning of the sui year.

Note

Bound lunar calendar

The lunar year nián is divided into months (月, yuè - "moon"), each corresponding to a lunar phase cycle. A lunar phase cycle (synodic month) lasts an average of 29.53 days, which is slightly shorter than the average interval between two zhongqi. A lunar year with 12 lunar months is about 354 days long, which is about 11 days shorter than the solar year. Every two or three years a thirteenth month (leap month) is inserted. This ensures that the beginning of the lunar year (Chinese New Year) always falls in the same season (between January 21 and February 21).

The present calendar has been in force since the reform of 1645, which was carried out with the help of the Jesuits (Adam Schall von Bell). It can be summarized in the following five rules:

1. The reference point is the meridian corresponding to the time zone of Beijing (today: 120°E).
2. The day begins at midnight.
3. The new moon always falls on the first day of the month.
4. The winter solstice in the northern hemisphere always falls on the 11th month.
5. If a leap month is necessary, it is the first month between two winter solstices on which no zhongqi falls.

The first month of the year is called Zhēngyuè (正月), the other months are numbered from 2 to 12. The 12th month is also called Làyuè (臘月 / 腊月). A leap month is given the same number as the previous month; for example, if the leap month follows the second month (二月, èryuè), then it is called the "additional second month" (閏二月 / 闰二月, rùn'èryuè). 19 solar years correspond almost exactly to 235 lunar revolutions (meton cycle). Therefore, a total of 7 leap months are inserted in every 19 years (19 × 12 + 7 = 235). The leap months are predominantly in the summer half-year, because due to the elliptical orbit of the earth with perihelion passage at the beginning of January the year divisions are run through faster in the winter half-year.

The months have 29 days (小月, xiǎo yuè - "short month") or 30 days (大月, dà yuè - "long month"). The days are numbered consecutively. A year with 12 months is usually 354, rarely 353 or 355 days long; a year with leap month is usually 384, rarely 383 or 385 days long.

The calculation of the Chinese calendar is so complicated because it is not based on the mean values, but on the exact astronomical positions of the moon and the sun. While in the Gregorian calendar and in the Jewish lunisolar calendar the leap years follow a fixed rhythm and the leap days or ‑months as well as the length of the individual months are fixed, this is not the case ‑in the Chinese calendar. Moreover, the synodic month varies between 29.27 and 29.84 days and is sometimes longer than the time interval between two zhongqi (29.45 ... 31.45 days). Therefore, it happens in rare cases that two zhongqi fall on one month or that no zhongqi falls on one month but it is not a leap month.

The following table gives the Gregorian date of the beginnings of the months for the period 2019-2022:

For the calculation of time (date, counting of years) the lunar calendar was used.

Government (era)

The counting of the (lunar) years was based on the emperor's reign. Upon ascending the throne, the emperor proclaimed a governmental deed, which traditionally consisted of two characters. Often, an emperor would also issue additional governing decrees during the course of his reign. With each governing vise, a new era began with its own counting of years. Year 1 was called yuan (元, yuán - "origin"). The last era (民國 / 民国, mínguó - "republic") was proclaimed after the end of the imperial period and is still used today in the Republic of China on Taiwan. Chinese president and military ruler Yuan Shikai's attempt to establish a new era called Hongxian in 1916 failed after 83 days. On March 23, 1912, the year Hongxian 1 was declared over and renamed back to Minguo 5.

The 60-year cycle

The years follow a cycle that runs for 60 years. It is composed of a cycle of the ten celestial stems (天干, tiāngān) and the twelve earth branches (地支, dìzhī), better known as the twelve animal signs. There are 60 combinations of trunk and branch (干支, gānzhī) - also called jiǎzǐ, 甲子 after the first combination. This cycle was independent of the dynasty in question and therefore more reliable in the event of a change of dynasty.