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The traditional Chinese calendar is a lunisolar calendar which reckons years, months and days according to astronomical phenomena. Currently, the Chinese calendar is defined by GB/T 33661-2017 Calculation and promulgation of the Chinese calendar, which is issued by the Standardization Administration of the People's Republic of China on May 12, 2017.
The Chinese calendar is used for traditional activities in China and overseas Chinese communities. It depicts and lists the dates of traditional Chinese holidays, and guides Chinese people in selecting the most auspicious days for weddings, funerals, moving, or beginning a business.
In the Chinese calendar, the days begin and end at midnight. The months begin on the day with the dark (new) moon. The years begin with the dark moon near the midpoint between winter solstice and spring equinox. The solar terms are the important components of the Chinese calendar. In a month, there are one to three solar terms.
The currently used traditional Chinese calendar is the end result of centuries of evolution. Many astronomical and seasonal factors were added by ancient scientists, and people can reckon the date of natural phenomena such as the moon phase and tide upon the Chinese calendar. The Chinese calendar has over 100 variants, whose characteristics reflect the calendar's evolutionary path. As with Chinese characters, different variants are used in different parts of the Chinese cultural sphere.
In Korea, Vietnam, and the Ryukyu Islands, the Chinese calendar was adopted completely and evolved into Korean, Ryukyuan, and Vietnamese calendar, with the main difference being the use of different meridians which leads to some astronomical events falling on different dates in different countries and thus the same event may occasionally be assigned a different date in each of those calendars. The traditional Japanese calendar was also derived from the Chinese calendar, based on a Japanese meridian, however its official use in Japan was abolished in the early 20th century and its usage has mostly disappeared since then. Calendars in Mongolia and Tibet have absorbed elements from the Chinese calendar and elements from other systems, but they are not direct descendants of the Chinese calendar.
The official calendar in China is the Gregorian calendar, but the traditional Chinese calendar still plays an important role there. The Chinese calendar is known officially as the Agricultural Calendar (traditional Chinese: 農曆; simplified Chinese: 农历; pinyin: Nónglì),[a] but is often referred to by other names, such as the Former Calendar (traditional Chinese: 舊曆; simplified Chinese: 旧历; pinyin: Jiùlì), the Traditional Calendar (traditional Chinese: 老曆; simplified Chinese: 老历; pinyin: Lǎolì), or the Lunar Calendar (traditional Chinese: 陰曆; simplified Chinese: 阴历; pinyin: Yīnlì; literally: "yin calendar"). The Chinese calendar preserves traditional East Asian culture.
Although the month sequences of Chinese calendar is decided by the solar term, the Chinese calendar is not an agriculture calendar.
In ancient China, the calendars marked the name/stem – branch of the year, month names, month length flags (大/小=Long/Short), the stems of 1/11/21 (1/11/21 of each month are same in stem, use a character), the branches of 1/11/21, and the date/stem-branch/time of the solar terms in the month.
The concepts in the Chinese, Hindu, and Hebrew calendars:
The movements of the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn are the key references for calendar calculations. These are known as the seven luminaries.
The Big Dipper is regarded as the compass in the sky, and the handle's direction decides the season and solar month.
The stars are divided into 3 enclosures and 28 mansions according to the location in the sky. The mansions are named with 28 characters according to the shape.
The moon moves about 1 mansion per day. Therefore, the 28 mansions are used to count days too. In the Tang Dynasty, Yuan Tiangang (Chinese: 袁天罡) matched the 28 mansions, 7 luminaries and animal signs, such as horn-wood-flood dragon (Chinese: 角木蛟).
Several coding systems are used for some special circumstances in order to avoid ambiguity, such as continuous day or year count.
|Stem-branches||Heaven stems||Earthly branches|
In Modern China, people use the Western hour-minute-second system to divide time. In Ancient China, people used the shi-ke system to divide the time during the day and the geng-dian system to divide the time during the night.. For example:
In the Chinese calendar, the day begins at midnight and ends at the next midnight, but people tend to regard the days as beginning at dawn.
sss initial, sss 1 ke,..., sss 8 ke, such as wush 3 ke (the third ke after wush)
a.sss initial, a.sss 1 ke,..., a.sss 4 ke, p.sss initial, p.sss 1 ke,..., p.sss 4 ke, such as a.wush 3 ke (the third ke of wush), p.yinsh 4 ke (the fourth ke after yinsh)
ggg, ggg 1 point,..., ggg 5 point, such as sang 2 point (the second point after sang).
The Chinese appear to have adopted the seven-day week from the Hellenistic system by the 4th century, although by which route is not entirely clear. It was again transmitted to China in the 8th century by Manichaeans, via the country of Kang (a Central Asian polity near Samarkand).[b][c] It is the most predominantly used system in modern China.
Other than the seven-day week system, in ancient China, the days were grouped into 10-day weeks with the stems, 12-day weeks with the branches, or 9/10-day weeks (Chinese: 旬; pinyin: xún) with the date in the month.
The law during the Han dynasty (206 BC – AD 220) required officials of the empire to rest every five days, called mu (沐), while it was changed into 10 days in the Tang dynasty (AD 618 – 907), called huan (澣/浣) or xún (旬).
Months were almost three weeks long (alternating 29 and 30 days to keep in line with the lunation). As a practice, the months are divided into 3 xún. The first 10 days is the early xún (Chinese: 上旬), the middle 10 days is the mid xún (Chinese: 中旬), and the last 9 or 10 days is the late xún (Chinese: 下旬).
Markets in Japan followed the Chinese jun (旬) system; see Japanese calendar. In Korea, it was called "Sun" (순,旬).
In winter, there is also a 9-day cycle counting start from the winter solstice, which would last for 9 cycles until 81 days later when it is deemed as the end of winter.
Month is the time between the dark moon. In the early days, the month length was estimated, and balanced. In general, 15-months-cycles and 17-months-cycles alternated for compliance with the synodic month.
In different ages, the calendar use different major cycle, which contains several 15-months-cycles and 17-months-cycle. The synodic month of Taichu calendar is 2943/81 days, so the major cycle contains three 17-months-cycles and two 15-months-cycles.
In 7th century, the Wùyín Yuán Calendar of Tang dynasty in 7th century, the month length was determined by the real synodic month for the first time, instead of the cycling method, which mean month lengths is determined by observation and prediction starting from Tang dynasty, except a few brief period of time.[d]
Because astronomical observation is used to determine month length, date of the Chinese calendar corresponds to the moon phase.
As the beginning of every month is determined by the time when the new moon occur, thus other countries who have adopted the calendar and use time standard that are different from China to calculate their own version of the calendar could result in deviation. For instance, the first new moon in the year 1968 in Gregorian calendar happened in UTC Jan 29 16:29, which would translate to Jan 29 23:29 in UTC+7 timezone (which is what North Vietnam used to calculate their Vietnamese calendar) while it would be Jan 30 00:15 based on the longitude of Beijing (as used by South Vietnam at the time), causing the two countries celebrate Tết holiday in different date that year and result in asynchronized attacks in Tet Offensive.
In ancient China, the solar year and solar terms were estimated and balanced, and the solar term is just the 1/24 of the solar year, about 157/32 days.
Starting from the 17th century, when the Shixian Calendar of Qing dynasty was adopted, the solar year was determined by the real tropical year instead. The solar terms correspond to intervals of 15° along the ecliptic.
Different version of traditional Chinese calendar might have different average year length. For instance, one solar year of Taichu calendar, which were implemented in 1st century BC, is 365385/1539 days, while one solar year of Shoushi calendar, which were implemented in 13th century, is 36597/400 days, which is the same as the Gregorian calendar.
Couples of solar terms are climate terms (solar months). The first of each couples is "pre-climate" (traditional Chinese: 節氣; simplified Chinese: 节气; pinyin: Jiéqì), and the second of the each couple is "mid-climate" (traditional Chinese: 中氣; simplified Chinese: 中气; pinyin: Zhōngqì).
In general, there are 11 or 12 complete months and 2 incomplete months, which contains the winter solstice, in a solar year. The 11 mid-climates except the winter solstice are in the 11 or 12 complete months. The first month without a mid-climate is the leap month.
The complete months except the intercalary month, queues up from 0 to 10, and the incomplete months follows this queue, to be 11. The intercalary follows the queue number before by rule.
The civil year starts from the first spring month (1), and ends at the last winter month (0/0i). The first and last month is called as Zhēngyuè (Chinese: 正月, capital month) and Làyuè (traditional Chinese: 臘月; simplified Chinese: 腊月, sacrificial month), and the other month is called according to the queue number (except that the 0th month is Shieryue, if the Layue is a leap month).
There are 12 or 13 months in each year. The years with 12 months, or 353~355 days, are common years. The years with 13 months, or 383~385 days, are long years.
Years were numbered after the reign title in Ancient China, but the reign title was no longer used after the founding of PRC in 1949. People use the stem-branches to demarcate the years. For example, the year from February 8, 2016 to January 27, 2017 is a Bǐngshēnnían, 13 months or 384 days long.
To Encode the date in the Chinese calendar, the flag of the intercalary month should be considered. For example, Run Liuyue 6, Dingyounian: 408-6i-06 (Timestamp: 40806106)
In Tang Dynasty, the earthly branches are used to mark the months for about 150 days (Dec, 761~May, 762).[e] At that time, the year starts from the month with Winter Solstice, and the month from Zhengyue to Layue are named as: Yinyue, Maoyue, Chenyue, Siyue, Wuyue, Weiyue, Shenyue Youyue, Xuyue, Haiyue, Ziyue, and Chouyue.
A typical graphical representation of the Chinese calendar is the vernal cattle diagram (traditional Chinese: 春牛圖; simplified Chinese: 春牛图), which help people calculate the date. In the vernal cattle diagram:
In China, age for official use is based on the Gregorian calendar. For traditional use, age is based on the Chinese calendar. For the first year from the birthday, the child is considered one year old. After each New Year's Eve, add one year. "Ring out the old age and ring in the new one (traditional Chinese: 辭舊迎新; simplified Chinese: 辞旧迎新; pinyin: cíjiù yíngxīn)" is the literary express of New Year Ceremony. For example, if one's birthday is Làyuè 29th 2013, he is 2 years old at Zhēngyuè 1st 2014. On the other hand, people say months old instead of years old, if someone is too young. It is that the age sequence is "1 month old, 2 months old, ... 10 months old, 2 years old, 3 years old...".
After the actual age (traditional Chinese: 實歲; simplified Chinese: 实岁) was introduced into China, the Chinese traditional age was referred to as the nominal age (traditional Chinese: 虛歲; simplified Chinese: 虚岁). Divided the year into two halves by the birthday in the Chinese calendar,[f] the nominal age is 2 older than the actual age in the first half, and the nominal age is 1 older than the actual age in the second half (traditional Chinese: 前半年前虛兩歲，後半年虛一歲; simplified Chinese: 前半年前虚两岁，后半年虚一岁).[g]
Just as it is awkward to define the birthday of someone born on the 29th of February in the Gregorian calendar, special rules are used for birthdays or other anniversaries during the intercalary month or on the 30th day.
In the Ancient China, years were numbered from 1, beginning when a new emperor ascended the throne or the current emperor announced a new era name. The first reign title was Jiànyuán (Chinese: 建元; literally: "era establishment", from 140 BCE), and the last reign title was Xuāntǒng (traditional Chinese: 宣統; simplified Chinese: 宣统, from 1908 CE). The era system was abolished in 1912 CE, after which the Current Era or Republican era was used. The epoch of the Current Era is just the same as the era name of Emperor Ping of Han, Yuánshí (Chinese: 元始; literally: "era beginning").
The 60 stem-branches were used to mark the date continually from Shang Dynasty. Before Han Dynasty, people knew the orbital period of Jupiter is about 4332 days, which is about 12*361 days. So, the orbital period of Jupiter was divided into 12 periods, which was used to number the year. The Jupiter was called as the star of age (traditional Chinese: 嵗星; simplified Chinese: 岁星; pinyin: suìxīng), and the 1/12 Jupiter orbital period was called as the age (traditional Chinese: 嵗; simplified Chinese: 岁; pinyin: suì).
361 days is just 6 cycles of 60-stem-branches, so the stem-branches of the first day move forward one after each sui. The first day of each sui was called as the sui capital (traditional Chinese: 太嵗; simplified Chinese: 太岁; pinyin: tàisuì).
And the stem-branches of the taisui was used to mark the year. Obviously, there're two taisui in some year for the sui is shorter than solar rear. About after each 86 year, a taisui was leaped. The leaped of the sui was called as beyond the star (Chinese: 超辰; pinyin: chāochén).
At the eastern Han Dynasty, the chaochen are abolished, and the 60 stem-branches are used to mark year continually without leap.
The Stem-branches year number system provided a solution for the defect of era system (unequal length of the reign titles)
Occasionally, nomenclature similar to that of the Christian era has been used, such as
No reference date is universally accepted.
On January 2, 1912, Sun Yat-sen declared a change to the official calendar and era. In his declaration, January 1, 1912 is called Shíyīyuè 13th, 4609 AH which assumes an epoch (1st year) of 2698 BCE. This declaration was adopted by many overseas Chinese communities outside Southeast Asia such as San Francisco's Chinatown.
In the 17th century, the Jesuits tried to determine what year should be considered the epoch of the Han calendar. In his Sinicae historiae decas prima (first published in Munich in 1658), Martino Martini (1614–1661) dated the ascension of the Yellow Emperor to 2697 BC, but started the Chinese calendar with the reign of Fuxi, which he claimed started in 2952 BCE. Philippe Couplet's (1623–1693) Chronological table of Chinese monarchs (Tabula chronologica monarchiae sinicae; 1686) also gave the same date for the Yellow Emperor. The Jesuits' dates provoked great interest in Europe, where they were used for comparisons with Biblical chronology.
Modern Chinese chronology has generally accepted Martini's dates, except that it usually places the reign of the Yellow Emperor in 2698 BC and omits the Yellow Emperor's predecessors Fuxi and Shennong, who are considered "too legendary to include".
Starting in 1903, radical publications started using the projected date of birth of the Yellow Emperor as the first year of the Han calendar. Different newspapers and magazines proposed different dates. Jiangsu, for example, counted 1905 as year 4396 (use an epoch of 2491 BCE), whereas the newspaper Ming Pao (traditional Chinese: 明報; simplified Chinese: 明报) reckoned 1905 as 4603 (use an epoch of 2698 BCE). Liu Shipei (劉師培; 1884–1919) created the Yellow Emperor Calendar, now often used to calculate the date, to show the unbroken continuity of the Han race and Han culture from earliest times. Liu's calendar started with the birth of the Yellow Emperor, which he determined to be 2711 BC. 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.
There is an epoch for each version of the Chinese calendar, which is called Lìyuán (traditional Chinese: 曆元; simplified Chinese: 历元). The epoch is the optimal origin of the calendar, and it is a Jiǎzǐrì, the first day of a lunar month, and the dark moon and solstice are just at the midnight (Chinese: 日得甲子夜半朔旦冬至). And tracing back to a perfect day, such as that day with the magical star sign, there's a supreme epoch (Chinese: 上元; pinyin: shàngyuán). The continuous year based on the supreme epoch is shàngyuán jīnián (traditional Chinese: 上元積年; simplified Chinese: 上元积年). More and more factors were added into the supreme epoch, and the shàngyuán jīnián became a huge number. So, the supreme epoch and shàngyuán jīnián were neglected from the Shòushí calendar.
Shao Yong (Chinese: 邵雍 1011–1077), a philosopher, cosmologist, poet, and historian who greatly influenced the development of Neo-Confucianism in China, introduced a time system in his The Ultimate which Manages the World (traditional Chinese: 皇極經世; simplified Chinese: 皇极经世; pinyin: Huángjíjīngshì)
In his time system, 1 yuán (Chinese: 元), which contains 12'9600 years, is a lifecycle of the world. Each yuán is divided into 12 huì (traditional Chinese: 會; simplified Chinese: 会). Each huì is divided into 30 yùn (traditional Chinese: 運; simplified Chinese: 运), and each yùn is divided into 12 shì (Chinese: 世). So, each shì is equivalent to 30 years. The yuán-huì-yùn-shì corresponds with nián-yuè-rì-shí. So the yuán-huì-yùn-shì is called the major tend or the numbers of the heaven, and the nián-yuè-rì-shí is called the minor tend or the numbers of the earth.
The minor tend of the birth is adapted by people for predicting destiny or fate. The numbers of nián-yuè-rì-shí are encoded with stem-branches and show a form of Bāzì. The nián-yuè-rì-shí are called the Four Pillars of Destiny. For example, the Bāzì of the Qianlong Emperor is Xīnmǎo, Dīngyǒu, Gēngwǔ, Bǐngzǐ (辛卯、丁酉、庚午、丙子). Shào's Huángjíjīngshì recorded the history of the timing system from the first year of the 180th yùn or 2149th shì (HYSN 0630-0101, 2577 BC) and marked the year with the reign title from the Jiǎchénnián of the 2156th shì (HYSN 0630-0811, 2357 BC, Tángyáo 1, traditional Chinese: 唐堯元年; simplified Chinese: 唐尧元年). According to this timing system, 2014-1-31 is HYSN/YR 0712-1001/0101.
The table below shows the kinds of year number system along with correspondences to the Western (Gregorian) calendar. Alternatively, see this larger table of the full 60-year cycle.
|Year in cycle||s,b||Gānzhī (干支)||Year of the...||CE||AR||HYSN||AH||Begins|
|27||7,3||gēngyín (庚寅)||Metal Tiger||2010||99||0712-0927||4707||February 14|
|28||8,4||xīnmǎo (辛卯)||Metal Rabbit||2011||100||0712-0928||4708||February 3|
|29||9,5||rénchén (壬辰)||Water Dragon||2012||101||0712-0929||4709||January 23|
|30||10,6||guǐsì (癸巳)||Water Snake||2013||102||0712-0930||4710||February 10|
|31||1,7||jiǎwǔ (甲午)||Wood Horse||2014||103||0712-1001||4711||January 31|
|32||2,8||yǐwèi (乙未)||Wood Goat||2015||104||0712-1002||4712||February 19|
|33||3,9||bǐngshēn (丙申)||Fire Monkey||2016||105||0712-1003||4713||February 8|
|34||4,10||dīngyǒu (丁酉)||Fire Rooster||2017||106||0712-1004||4714||January 28|
|35||5,11||wùxū (戊戌)||Earth Dog||2018||107||0712-1005||4715||February 16|
|36||6,12||jǐhài (己亥)||Earth Pig||2019||108||0712-1006||4716||February 5|
1 As of the beginning of the year. AR=Anno the Republic of China
2 Timestamp according to Huángjíjīngshì, as a format of Huìyùn-Shìnián.
3 Huángdì era, using an epoch (year 1) of 2697 BC. Subtract 60 if using an epoch of 2637 BC. Add 1 if using an epoch of 2698 BC.
In the Sinosphere, the traditional festivals are calculated using the date or solar terms, and are considered auspicious.
|Festival||English||Define||Original Define (Han Dynasty)||Date of the following...||Remark|
|Major traditional festivals on fixed date|
|Làyuè 8||The third Xuri (戌) after the Winter Solstice||2017-01-05|
|the cleanup day before New Year's Week|
New Year's Eve
|the last day of the year, Làyuè 29 or 30||2017-01-27||a statutory holiday|
New Year's Day
|The first day of the year, Zhēngyuè 1||2017-01-28||a statutory holiday|
|Zhēngyuè 15||The first full moon of the year||2017-02-11||Also called as Yuanxiao (the night of the first full moon), an annual carnival in ancient China|
|Sānyuè 3||The first Siri (巳) of Sanyue||2017-03-30||a version of Qingmin Festival, The origin of Thailand water splashing festival|
|Sìyuè 8||2017-05-03||a statutory holiday in Hong Kong SAR|
Dragon Boat Festival
|Wǔyuè 5||The First Wuri (午) of Wuyue||2017-05-30||a statutory holiday|
|Qīyuè 7||2017-08-28||Ingenuity Maiden's Day|
|Qīyuè 15||The full moon at the mid-year||2017-09-05||the worship of ancestors|
|Bāyuè 15||The full moon at the mid-autumn||2017-10-04||Reunion Day, a statutory holiday|
|Jiǔyuè 9||2017-10-28||Regarded as Elder's Day in China
a statutory holiday in Hong Kong SAR
|Shíyuè 1||The New Year's Day of Qin Calendar||2017-11-18||Issue Royal calendar (almanac) for the following year.|
|Shíyuè 15||The first full moon in Qin calendar||2017-12-02||the worship of worthy|
|Major traditional festivals on solar term|
|Beginning of Spring||The day that Spring commences
about February 4
|The day of the Stimulation of Agriculture|
|Cold Food Festival||the 105th day after the Winter Solstice
about April 4
|Sānyuè 7, 2017
|The fast before the worship of ancestors at Qingming Festival.|
|Qingming Festival||The day of the solar term of Bright and Clear
about April 5
|Sānyuè 8, 2017
|The day of the worship of ancestors, a statutory holiday|
|Winter Solstice||The day of the Winter Solstice
about December 21
|Shíyīyuè 5, 2017
|The node of the solar years|
|Spring/Autumn Pray||the fifth Wùrì (戊) after Spring/Autumn Commences||March 21
|a version of Spring/Autumn equinox|
|The traditional business festivals|
|Zhēngyuè 5||In the old days, merchants used to open their stores from Zhēngyuè 5, and host a prayer service on that day. God of Wealth's Day, which the prayer service is called God of Wealth is Welcome.|
Touya & Weiya
|Èryuè 2 / Làyuè 16||In the Ancient China, business owners hosted the Yaji rites (Chinese: 牙祭; pinyin: Yaji) at the 2nd and 16th day of each month from Eryue to Layue, to reward the local guardian god and their employees. The First/Last Thanksgiving rite is hold on Èryue 2/Làyuè 16.|
Before the Zhou dynasty, the Chinese calendars used a solar calendar.
According to Ancient Chinese literature, the first version was the five-phases calendar (traditional Chinese: 五行曆; simplified Chinese: 五行历), which came from the tying knots culture. In the five-phases calendar, a year was divided into five phases which were expressed by five ropes. Each rope was folded into halves, and the day in the corner was the capital day (traditional Chinese: 行禦; simplified Chinese: 行御). They're three sections in each halves, and the Chinese Character of phase is the pictograph of the rope of the tying knots. The ten half-ropes were arranged into a row, and a man shape was engraved by the ropes. The part of man shape derived into 10 heaven stems. The days in each sections were recorded with 12 earthly branches. So, in the five-phases calendar, a year is fives phases or ten months, and a phase is six sections or 73 days. The remainder of each phases are marked in the Hetu, which is found in Song Dynasty.
The second version is the four-seasons calendar (traditional Chinese: 四時八節曆; simplified Chinese: 四时八节历). In the four-seasons calendar, the days were counting by ten, and three ten-days weeks were built into a month. There were 12 months in a year, and a week were intercalated in the hot month. In the age of four-seasons calendar, the 10 heaven stems and 12 earthly branches were used to mark days synchronously.
The third version is the balanced calendar (traditional Chinese: 調曆; simplified Chinese: 调历) a year was defined into 365.25 days, and the month was defined into 29.5 days. And after each 16 months, a half-month was intercalated. There half-months were merged into months later, and the archetype of the Chinese calendar was brought out in the Spring and Autumn ages.
Oracle bone records indicate that the calendar of Shang Dynasty were a balanced calendar, and the 12, 13, even 14 months were packed into a year roughly. Generally, the month after the winter solstice was named as the capital month (Chinese: 正月).
In Zhou dynasty, the authority issued the official calendar, which is a primitive lunisolar calendar. The year beginning of Zhou's calendar (traditional Chinese: 周曆; simplified Chinese: 周历) is the day with dark moon before the winter solstice, and the epoch is the Winter Solstice of a Dīngyǒu year.
Some remote vassal states issued their own calendars upon the rule of Zhou's calendar, such as:
These six calendars are called as the six ancient calendars (traditional Chinese: 古六曆; simplified Chinese: 古六历), and are the quarter remainder calendars (traditional Chinese: 四分曆; simplified Chinese: 四分历; pinyin: sìfēnlì). The months of these calendars begin on the day with the darkmoon, and there are 12 or 13 month within a year. The intercalary month is placed at the end of the year, and called as 13th month.
The modern version of the Zhuanxu's calendar is the Chinese Qiang calendar and Chinese Dai calendar, which are the calendar of mountain peoples.
After Qin Shi Huang unified China under the Qin dynasty in 221 BCE, Qin's calendar (traditional Chinese: 秦曆; simplified Chinese: 秦历) was promulgated. The Qin's calendar follows the rules of Zhuanxu's calendar, but the month order follows the Xia calendar. The months in the year are from the 10th month to the 9th month, and the intercalary month is called as the second Jiuyue (traditional Chinese: 後九月; simplified Chinese: 后九月). In the early Han dynasty, the Qin calendar continued to be used.
Emperor Wu of the Han dynasty introduced reforms halfway through his administration. His Taichu or Grand Inception Calendar (traditional Chinese: 太初曆; simplified Chinese: 太初历) introduced 24 solar terms which determined the month names. The solar year was defined as 365 385/1539 days, and divided into 24 solar terms. Each couples of solar terms are associated into 12 climate terms. The lunar month was defined as 29 43/81 days and named according to the closest climate term. The mid-climate in the month decides the month name, and a month without mid-climate is an intercalary month.
The Taichu calendar established the frame of the Chinese calendar, Ever since then, there have been over 100 official calendars in Chinese which are consecutive and follow the structure of Tàichū calendar both. There're several innovation in calendar calculation in the history of over 2100 years, such as:
The Chinese calendar lost the status of the official statutory calendar in China in the beginning of the 20th century, however it has been continually being used for various purposes.
Because the Republic of China adopted the UTC+8 timezone instead of using Beijing Mean Solar Time in 1928 CE, Chinese calendars produced in Mainland China have switched to use UTC+8 in the following year. However, the switch in time standard used in Chinese calendars has not been universally adopted in areas like Taiwan and Hong Kong, and some calendars were still follow the last calendar of Qing dynasty that was published in 1908. In 1978, this practice caused confusion on what date the 1978 Mid-autumn festival occur, and caused those areas to switch to the UTC+8-based Chinese calendar thereafter.
In the late Ming dynasty, Xu Guangqi and his colleagues worked out the new calendar based on western astronomical arithmetic. But the new calendar was not released before the end of the Ming dynasty. In the early Qing dynasty, Johann Adam Schall von Bell submitted the calendar to the Shunzhi Emperor. The Qing government released the calendar under the name the Shíxiàn calendar, which means seasonal charter. In the Shíxiàn calendar, the solar terms each correspond to 15° along the ecliptic. It meant the Chinese calendar can be used as astronomical calendar. However, the length of the climate term near the perihelion is shorter than 30 days and there may be two mid-climate terms. The rule of the mid-climate terms decides the months, which is used for thousands years, lose its validity. The Shíxiàn calendar changed the rule to "decides the month in sequence, except the intercalary month."
The version of the traditional Chinese calendar currently being used follows the rules of the Shíxiàn calendar, except that:
To optimize the Chinese calendar, astronomers have released many proposed changes. A typical proposal was released by Gao Pingzi (Chinese: 高平子; 1888-1970), a Chinese astronomer who was one of the founders of Purple Mountain Observatory. In his proposal, the month numbers are calculated before the dark moons and the solar terms were rounded to the day. Under his proposal, the month numbers are the same for the Chinese calendar upon different time zones.
As the intercalary month is determined by the first month without mid-climate and the exact time when each mid-climate happen would vary according to time zone, countries that have adopted the calendar but calculate with their own time could vary from the one used in China because of this. For instance, the 2012 FTG happened in UTC May 20 15:15, which would translate to May 20 23:15 in UTC+8, making FTG the mid-climate for the fourth month of that traditional Chinese year [April 21 ~ May 20 in Gregorian calendar], but in Korea it happened in May 21 00:15 in UTC+9, and as new moon take place in May 21 in that month, therefore the month before that would only consist of the SC solar term, lacking mid-climate. As a result, the month starting at April 21 would be an intercalary month in Korean calendar, but not in Chinese Calendar, and the intercalary month in Chinese calendar would start in the month after, in the fifth month starting from May 21, which would only consist of the solar term STG, while the month in Korean Calendar would have both FTG and STG solar term in it.
Among the ethnic groups inhabiting the mountains and plateaus of southwestern China, and those living in the grasslands of northern China, their civil calendars show a diversity of practice based upon their characteristic phenology and culture, but they are based on the algorithm of the Chinese calendar of different periods, especially those of the Tang dynasty and pre-Qin dynasty period.