The Chinese Calendar, Calendar in Japan and Vietnam

Chinese Calendar

Overview

Although there have been many dynasties, empires, and revolutions in China since the Bronze Age, Chinese history shows a remarkable continuity not found elsewhere. The 1911 revolution ended over 2000 years of history of the Chinese Empire. The republican government introduced the Gregorian calendar in 1912. However, the traditional Chinese calendar remains in use by the people until today. The calendar is used in other countries, like Japan and Vietnam in a similar form, which shows the once great influence of the Chinese Empire in East Asia.

History of the Calendar

We know oracle bones from the Shang period (c. 1600 BCE - 1100 BCE) showing evidence of a calendar having been used then, the days having been counted within a sexagesimal cycle. In the Zhou period (c. 1100 BCE - 221 BCE) the years were also designated in that manner. The length of the tropical year was taken to be 365.25 days, while the value for the length of a synodic month was given as 29.5 days. During last chapter of the Zhou period, known as the period of the "Fighting Empires", a calendar very similar to the modern Chinese calendar was in use. A year consisted of 12 lunar months of 29 or 30 days. A 13th month was inserted from time to time. A month began on the day of the new moon and was divided into three decades. During the reign of the first Qin emperor Shihuang Di (r. 221 BCE - 210 BCE) the beginning of the year was shifted one month back. For agricultural purposes there were 24 solar terms defined by the sun's movement through 24 sections defined along the ecliptic.

Another reform was implemented in 104 BCE during the Han dynasty. This reform shifted the beginning of the year in such a way that the winter solstice always occurred in the 11th month now. Although deviations from this rule are known from later times (the last one in 761) it is valid still today. Together with the shifted New Year an improved value for the mean length of a synodic month of 29⁴³/₈₁ days was adopted which is astonishingly exact. The 24 solar terms of the agricultural calendar served to define rules on when to insert a leap month.

A difference between the sidereal and tropical years was suspected by Chinese astronomers first at the end of the Han dynasty. It was eventually proven in the 4th century, thus discovering the precession of the vernal equinox.

From 619 on true new moons were used rather than mean ones. Later, in 1281, another reform gave the tropical year a mean length of 365.2425 days. Thus the Chinese calendar was as exact as the Gregorian calendar 300 years before the introduction of the latter. Instead of this mean value the Chinese calendar started to use true solar months in 1645.

Until today both the traditional lunisolar and solar calendars are in use. Officially though the Gregorian calendar is used in China since 1912.

Solar Calendar

A solar calendar dividing the year into 24 solar terms was developed under the Qin dynasty already. The terms were named after meteorological phenomena or agricultural works of their respective time in the year. There are major terms (zhongqi) and minor terms (jieqi) arranged alternatingly. The following table shows the terms's names and approximate Gregorian dates of the terms, the main terms being marked with an asterisk (*).

The sections of the ecliptic all cover the same angle of 15° while the apparent sun is moving at a slighty varying speed during one year. Thus the time the sun takes to travel through one section varies between c. 29.5 and 31.4 days.

Years are not counted in this solar calendar. Today, the solar terms are mainly used for determining when to insert a leap month in the lunisolar calendar.

Lunisolar Calendar

The lunisolar calendar year has 12 months in common years and 13 months in leap years. The determination of when to consider a month intercalary are reminiscent of the respective rules of Indian calendars. While Indian calendars aim to reconcile lunar year and sidereal year, the Chinese calendar combines the lunar year with the tropical year.

The first day of the month is the day on which the true new moon occurs. For practical reasons, calculations are made for the meridian of 120° East. The months are numbered from one to twelve within the year. The intercalary month in a leap year bears the same number as the preceding month, and is additionally marked as intercalary. Since a solar month is mostly longer than a lunar month sometimes a lunar months lies entirely within a solar month. That means that during this lunar month the sun does not enter a major solar term (zhongqi). The first such month in a year is considered intercalary. New Year is determined so that the winter solstice always occurs in the 11th month.

The designation of years in the Chinese calendar is reminiscent of the way days are named in the Mayan calendar. First, days were named in the sexagesimal cycle in China. But the system was adopted for naming years subsequently and later the system was used for years only. In the system ten Heavenly stems are combined with twelve Earthly branches, the sequence and names of which are shown in the following table.

A year is named with a combination of stem and branch. The first year is called Jia-Zi, a combination of first stem and first branch. The second year bears the name Yi-Chou combining the second stem with the second branch. Thus the third year is Bing-Yin, etc. After having reached the last stem or branch, the first stem/branch is used in the following year. With this system, designations repeat after 60 years, 60 being the least common multiple of 10 and 12. Although normally years or cycles are not counted, according to tradition the first year of the first cycle is taken to have begun in 2637 BCE. The current 78th cycle began in 1984. Often a year is just called by the corresponding zodiacal sign. The year of the pig thus began in February 2007.

Years were counted according to eras the reigning emperor chose at his own will, and mostly these counts were not regnal years. Only beginning the Ming dynasty, in the 14th century, the emperor declared an era beginning with the New Year after his accession and known by the posthumous name of the emperor. This dating by a kind of regnal years only ended when the last emperor was overthrown. The government of the Chinese republic adopted the Gregorian calendar on 1 January 1912, but with a different era. Instead of using the Christian era, the Minguo era (era of the Republic) was introduced, beginning on 1 January 1912. In mainland China, the Christian era was introduced in 1949, while on Taiwan the Minguo era is official still today. The year Minguo 99 corresponds to the Gregorian year 2010.

Holidays

There are many holidays celebrated throughout the Chinese year. New Years day, Yuandan, falls on the first New Moon after 20 January, i. e. between 21 January and 20 February and is celebrated with fireworks. Some other feast days are or were

• Dengjie (Lantern Feast) on the 15th day of the first month,
• Duanyang on the 5th day of the 5th month,
• Diuzhen (Laying Down Needles) on the 7th day of the 7th month, and
• Zhongqiujie (Mid Autumn) on the 15th day of the 8th month.

Japanese Calendar

Both Chinese calendars, i. e. solar and lunisolar calendars, were taken over by the Japanese.

Solar Calendar

The year was divided into 12 terms (setsu) whicht in turn were divided into two halves each. The beginning of the first half was called sekki, while the name of the beginning of the second half was chūki. The half-month from sekki to chūki thus corresponded to the Chinese minor term (jieqi) and the half-month between chūki and sekki was equal to the Chinese major term (zhongqi). The latter ones are marked with an asterisk (*) in the following table.

Lunisolar Calendar

The Japanese lunisolar calendar follows the Chinese in structure and leap year rules. The method of determining an intercalary month was taken over from China in 604. Later reforms carried out in China were subsequently introduced also in Japan, although with a sometimes considerable delay of years or even centuries. Japanese calendar dates thus can differ from the respective Chinese dates by some days or a month.

Years are named within the same sexagesimal cycle as Chinese calendar years, using stems and branches. The names of the branches and their corresponding animals can be seen in the following table.

Besides the sexagesimal cycle other systems of designating years were in use. Regnal years were employed according to the system in China, beginning the count with the first complete calendar year after the accession. Later official eras, called Nengō, were declared by the imperial court at certain events like the accession of a new emperor, other notable events, or auspicious years of the sexagesimal cycle. The first such era was named Taika (Great Reform) and was declared in 645. Subsequently, many Nengōs were introduced, many of them in use only for some years, some not lasting a year. Only since the restauration of imperial rule in 1868 a new era is declared only with the accession of a new emperor, this era then lasting until the end of the emperor's reign. The years correspond to Gregorian calendar years since its introduction in 1873. The era declared when Hirohito became emperor bears the name Shōwa and lasted from 1926 (= Shōwa 1) to 1989 (= Shōwa 64). With the accession of emperor Akihito in 1989 began the Hesei era. According to that era, the current Gregorian year 2010 is called Heisei 22. In the second half of the 19th century the Japanese National Era came into use. This era begins with the year 661 and was commonly used until the end of World War II with the words kigen (beginning of the dynasty) oder kōki (imperial era) added to distiguish this era from the Christian era.

Vietnamese Calendar

As in Japan and China, in Vietnam the Gregorian calendar is official. The Vietnamese calendar is used widely, however. The calendar came to Vietnam from China, is lunisolar, and has the same structure as the Chinese calendar. Years are named by a Heavenly cycle of 10 years and an Earthly cycle of 12 years, which results in the sexagesimal cycle known from the Chinese calendar. The names of the years of both cycles together with the respective animals are seen in the following table.

Other Calendars

The sexagesimal cycle of years are found in several further calendars, e. g. in Korea, Cambodia, Laos, and Thailand, with the Gregorian calendar in official use. In South East Asia the Indian influence can be told from the months's names derived from those of Indian calendars, and from the names of the days of the week from Sanskrit names.

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