Chinese calendar

The Chinese calendar is a lunisolar calendar created by or commonly used by the Chinese people. While this description is generally accurate, it does not provide a definitive or complete answer. A total of 102 calendars have been officially recorded in classical historical texts. In addition, many more calendars were created privately, with others being built by people who adapted Chinese cultural practices, such as the Koreans, Japanese, Vietnamese, and many others, over the course of a long history.
A Chinese calendar consists of twelve months, each aligned with the phases of the moon, along with an intercalary month inserted as needed to keep the calendar in sync with the seasons. It also features twenty-four solar terms, which track the position of the sun and are closely related to climate patterns. Among these, the winter solstice is the most significant reference point and must occur in the eleventh month of the year. Each month contains either twenty-nine or thirty days. The sexagenary cycle for each day runs continuously over thousands of years and serves as a determining factor to pinpoint a specific day amidst the many variations in the calendar. The variety of calendars arises from deviations in algorithms and assumptions about inputs. The Chinese calendar is location-sensitive, meaning that calculations based on different locations, such as Beijing and Nanjing, can yield different results.
While modern China primarily adopts the Gregorian calendar for official purposes, the traditional calendar remains culturally significant, influencing festivals and cultural practices, determining the timing of Chinese New Year with traditions like the twelve animals of the Chinese zodiac still widely observed. The winter solstice serves as another New Year, a tradition inherited from ancient China. Beyond China, it has shaped other East Asian calendars, including the Korean, Vietnamese, and Japanese lunisolar systems, each adapting the same lunisolar principles while integrating local customs and terminology.

Etymology

The name of calendar is in p=lì, and was represented in earlier character forms variants, and ultimately derived from an ancient form. The ancient form of the character consists of two stalks of rice plant, arranged in parallel. This character represents the order in space and also the order in time. As its meaning became complex, the modern dedicated character was created to represent the meaning of calendar.
There are various Chinese terms for the calendar including:

Nongli Calendar
Jiuli Calendar
Laoli Calendar
Zhongli Calendar
Huali Calendar

Various modern Chinese calendar names resulted from the struggle between the introduction of Gregorian calendar by government and the preservation of customs by the public in the era of Republic of China. The government wanted to abolish the Chinese calendar and use the Gregorian calendar, and even abolished the Chinese New Year, but faced great opposition. The public needed the astronomical Chinese calendar to do things at a proper time, for example farming and fishing; also, a wide spectrum of festivals and customs observations have been based on the calendar. The government finally compromised and rebranded it as the agricultural calendar in 1947, depreciating the calendar to merely agricultural use.

Year-numbering systems

Eras

Ancient China numbered years from an emperor's ascension to the throne or his declaration of a new era name. The first recorded reign title was, from 140 BCE; the last reign title was s=宣统, from 1908 CE. The era system was abolished in 1912, after which the current or Republican era was used.

Epochs

An epoch is a point in time chosen as the origin of a particular calendar era, thus serving as a reference point from which subsequent time or dates are measured. The use of epochs in Chinese calendar system allow for a chronological starting point from whence to begin point continuously numbering subsequent dates. Various epochs have been used. Similarly, nomenclature similar to that of the Christian era has occasionally been used:

Era	Chinese name	Start	Year 1	CE is year...
Yellow Emperor year	黄帝紀年	Yellow Emperor began reigning	2697 BCE or 2698 BCE	or
Yáo year	唐堯紀年	Emperor Yao began reigning	2156 BCE
Gònghé year	共和紀年	Gonghe Regency began	841 BCE
Confucius year	孔子紀年	Confucius's birth year	551 BCE
Unity year	統一紀年	Qin Shi Huang completes unification	221 BCE

No reference date is universally accepted. The most popular is the Gregorian calendar.
During the 17th century, the Jesuit missionaries tried to determine the epochal year of the Chinese calendar. In his Sinicae historiae decas prima, Martino Martini dated the Yellow Emperor's ascension at 2697 BCE and began the Chinese calendar with the reign of Fuxi.
Philippe Couplet's 1686 Chronological table of Chinese monarchs gave the same date for the Yellow Emperor. The Jesuits' dates provoked interest in Europe, where they were used for comparison with Biblical chronology. Modern Chinese chronology has generally accepted Martini's dates, except that it usually places the reign of the Yellow Emperor at 2698 BCE and omits his predecessors Fuxi and Shennong as "too legendary to include".
Publications began using the estimated birth date of the Yellow Emperor as the first year of the Han calendar in 1903, with newspapers and magazines proposing different dates. Jiangsu province counted 1905 as the year 4396, and the newspaper Ming Pao reckoned 1905 as 4603. Liu Shipei created the Yellow Emperor Calendar, with year 1 as the birth of the emperor. There is no evidence that this calendar was used before the 20th century. Liu calculated that the 1900 international expedition sent by the Eight-Nation Alliance to suppress the Boxer Rebellion entered Beijing in the 4611th year of the Yellow Emperor.
On 2 January 1912, Sun Yat-sen announced changes to the official calendar and era. 1 January was year 4809.11.14, assuming a year 1 of 2698 BCE, making CE year. Many overseas Chinese communities like San Francisco's Chinatown adopted the change.

History

Solar calendars

The traditional Chinese lunisolar calendar was developed between 771 BCE and 476 BCE, during the Spring and Autumn period of the Eastern Zhou dynasty. Solar calendars were used before the Zhou dynasty period, along with the basic sexagenary system.
One version of the solar calendar is the five-elements calendar, which derives from the Wu Xing. A 365-day year was divided into five phases of 72 days, with each phase preceded by an intercalary day associated with the claimed beginning of the following 72 day period of domination by the next Wu Xing element; thus, the five phases each begin with a governing-element day, followed by a 72-day period characterized by the ruling element. Years began on a day and a 72-day wood phase, followed by a day and a 72-day fire phase; a day and a 72-day earth phase; a day and a 72-day metal phase, and a day followed by a water phase. Each phase consisted of two three-week months, making each year ten months long. Other days were tracked using the Yellow River Map.
Another version is a four-quarters calendar. The weeks were ten days long, with one month consisting of three weeks. A year had 12 months, with a ten-day week intercalated in summer as needed to keep up with the tropical year. The 10 Heavenly Stems and 12 Earthly Branches were used to mark days.
A third version is the balanced calendar. A year was 365.25 days, and a month was 29.5 days. After every 16th month, a half-month was intercalated. According to oracle bone records, the Shang dynasty calendar was a balanced calendar with 12 to 14 months in a year; the month after the winter solstice was.
A solar calendar called the Tung Shing, the Yellow Calendar or Imperial Calendar continued to see use as an almanac and agricultural guide throughout Chinese history.

Lunisolar calendars by dynasty

Lunisolar calendars involve correlations of the cycles of the sun and the moon.

Zhou dynasty

The first lunisolar calendar was the Zhou calendar, introduced under the Zhou dynasty. This calendar sets the beginning of the year at the day of the new moon before the winter solstice.

Competing Warring states calendars

Several competing lunisolar calendars were introduced as Zhou devolved into the Warring States, especially by states fighting Zhou control during the Warring States period.
From the Warring States period, six especially significant calendar systems are known to have begun to be developed. Later on, during their future course in history, the modern names for the ancient six calendars were also developed: Huangdi, Yin, Zhou, Xia, Zhuanxu, and Lu.
Modern historical knowledge and records are limited for the earlier calendars. These calendars are known as the six ancient calendars, or quarter-remainder calendars,, since all calculate a year as days long. Months begin on the day of the new moon, and a year has 12 or 13 months. Intercalary months are added to the end of the year.
The state of Lu issued its own Lu calendar.
The state of Jin issued the Xia calendar with a year beginning on the day of the new moon nearest the March equinox.
The state of Qin issued the Zhuanxu calendar, with a year beginning on the day of the new moon nearest the winter solstice.
The Qiang and Dai calendars are modern versions of the Zhuanxu calendar, used by highland peoples.
The Song state's Yin calendar began its year on the day of the new moon after the winter solstice.