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History of Chinese Calendar

The legendary beginning of the Chinese calendar developed during the first millennium BC. The legend states that the first Chinese calendar was invented by the first legendary emperor, Huangdi or the Yellow Emperor, whose reign was assigned to 2698-2599 BC. The fourth legendary emperor, Emperor Yao, added the intercalary month. The 60-year stem-branch (gānzhī) cycle was first assigned to years during the first century BC. Giving Huangdi some maturity, the first year of the first cycle was assigned to 2637 BC according to Herbert A. Giles, A Chinese-English Dictionary (1912), and all other Western authors during the late Qing dynasty. Thus since 1984 the current cycle has been 78. However, some modern authors assign the first year of the first cycle to 2697 BC while Huangdi was still immature, saying we are now in cycle 79. These two epochs give rise to two continuous counts of years, causing the 'Chinese' years 4642 or 4702 to begin in early 2005.

However, continuously numbered sexagesimal cycles and the years based on them were inventions of Western chronologists—the Chinese themselves did not use either. But they did use unnumbered cycles, albeit in a subservient role to the reign-period year declared by the Emperor of China. Indeed, not using the emperor's reign-period was tantamount to treason punishable by death. But the Boxer rebellion of 1900 left the de facto ruler of China, the Empress Dowager Cixi, weakened and vulnerable to a challenge from Chinese Republicans, who intentionally used a continuous count of years to delegitimize the Qing Dynasty by refusing to use its years. Although republican newspapers used more than one epoch, that selected by Sun Yat-sen, 2698 BC, was adopted by most overseas Chinese communities outside southeast Asia like San Francisco's Chinatown, causing their year 4703 to begin in early 2005. Many chronologists, being unfamiliar with its history, think that 2698 BC is an error for the 2697 BC epoch obtained from sexagesimal cycles, whereas it is actually the only epoch actually used by some Chinese, albeit a minority (most Chinese don't use any continuous count of years from a legendary epoch).

Early History

The earliest archaeological evidence of the Chinese calendar appears on oracle bones of the late second millennium BC Shang dynasty. They show a 12-month lunisolar year having an occasional thirteenth month, and even a fourteenth month. Because Chinese dates are on firm ground beginning in 841 BC, the calendar of the early Zhou dynasty is known to have used arbitrary intercalations. The first month of its year was near the winter solstice and its intercalary month was after the twelfth month. The sìfēn (quarter remainder) calendar, which began about 484 BC, was the first calculated Chinese calendar, so named because it used a solar year of 365? days, along with a 19-year = 235-month Rule Cycle, known in the West as the Metonic cycle. The winter solstice was in its first month and its intercalary month was inserted after the twelfth month. Beginning in 256 BC with the Qin kingdom, which would later become the Qin dynasty, the intercalary month was an extra ninth month at the end of a year that began with the tenth month, now placing the winter solstice in the eleventh month. This year continued to be used during the first half of the Western Han Dynasty.

Development of Chinese Calendar

The calendar is closely related with the development of the astronomy. China is one of the first countries that see the emergence of astronomy, as well as the calendar. As far as 5,000 years ago, China had the lunisolar calendar, which indicated that each year had 366 days.

In the Shang Dynasty (1600-1066BC), officials were appointed to bear the sole task of observing and recording the changes in the heavens. During this period, people used the lunisolar calendar, with an intercalary added to the end of certain years. During the Western Zhou Dynasty (1066-771BC), the astronomer began to measure the shadow cast by the sun and decided upon 24 solar terms to direct the farming.

In the Western Han Dynasty (206BC-23AD), Emperor Wu ordered the establishment of a new calendar -- Taichu Calendar, based on the old calendar. And the calendar was used in the next 200 years. In the Eastern Han Dynasty (25-220), Sifen Calendar was drawn.

Later, Zu Chongzhi worked out the Daming Calendar, taking into consideration the precession of the equinoxes for the first time in China. After observations and studies, Zu concluded that a year lasted exactly 365.24281481 days which was only 52 seconds different from the modern estimate.

In the Tang Dynasty (618-907), famous monk Yi Xing compiled the Dayan Calendar, the most comprehensive and thorough calendar in the Chinese history. The almanac consisted of 7 parts, explaining in details how to calculate the new moon, full moon, 24 solar terms, the movement of the sun and the moon, etc. The calendar had great influences as all the later ones were revised according to it before the introduction of western calendar.

In the Northern Song Dynasty (960-1127), Shen Kuo worked out the 12 Qijie Calendar, discarding the intercalary and this is in line with the Gregorian Calendar.

During the Yuan Dynasty (1279-1368), Guo Shoujing compiled the Shoushi Calendar. He employed several methods of calculation, including interpolation, spherical trigonometry to solve four main problems in the previous calendars. His calendar had 365.2425 days in a year, which was only 26 seconds different from the time it takes the earth to go around the sun. His achievement was 300 years earlier than the finalization of the modern calendar.

From the Ming Dynasty (1368-1644), Jesuit missionaries brought European astronomy to China. In the early Qing Dynasty (1644-1911), German missionary Johann Adam Schall von Bell compiled the Shixian Calendar. From 1912, China began to adopt the Gregorian Calendar, but the traditional Chinese lunar calendar was still in use. In essence, the lunar calendar was Shixian Calendar.

The "No Principal Term" Rule

The great Emperor Wu of the Western Han dynasty introduced the basic rules that have governed the Chinese calendar ever since. His Tàichū (Grand Inception) calendar of 104 BC had a year with the winter solstice in the eleventh month and designated as intercalary any calendar month (a month of 29 or 30 whole days) during which the sun does not pass a principal term (remained within the same sign of the zodiac throughout). Because the sun's mean motion was used to calculate the jiéqì until 1645, this intercalary month was equally likely to occur after any month of the year. However, the conjunction of the sun and moon (the astronomical new moon) used the mean motions of both the sun and moon only until 619, the second year of the Tang dynasty, when both began to use true motions modeled using two offset opposing parabolas (with small linear and cubic components). Unfortunately, the parabolas did not meet smoothly at the mean motion, but met with a discontinuity or jump.

The True Sun and Moon

With the introduction of Western astronomy into China via the Jesuits, the motions of both the sun and moon began to use sinusoids in the 1645 Shíxiàn (Constant Conformity) calendar of the Qing dynasty, made by the Jesuit Adam Schall. The true motion of the sun was now used to calculate the jiéqì, which caused the intercalary month to often occur after the second through the ninth months, but rarely after the tenth through first months. A few autumn-winter periods have one or two calendar months where the sun enters two signs of the zodiac, interspersed with two or three calendar months where the sun stays within one sign.

The Gregorian Reform and the 1929 Time Change

The Gregorian calendar was adopted by the nascent Republic of China effective January 1, 1912 for official business, but the general populace continued to use the traditional calendar of the Qing Dynasty. The status of the Gregorian calendar between about 1916 and 1921 while China was controlled by several competing warlords is unknown. From about 1921 until 1928 warlords continued to control northern China, but the Kuomintang controlled southern China and probably used the Gregorian calendar. After the Kuomintang declared a reconstituted Republic of China October 10, 1928, they decreed that effective 1 January 1929, everyone must use the Gregorian calendar. They also decreed that effective 1 January 1929, all of China must use the coastal time zone that had been used by all European treaty ports along the Chinese coast since 1904. This changed the beginning of each calendar day, for both the traditional and Gregorian calendars, by +14.3 minutes from Beijing midnight to midnight at the longitude 120° east of Greenwich.

This caused some discrepancies, such as with the 1978 Mid-Autumn Festival. There was a new moon on September 3, 1978, at 00:07, Chinese Standard Time[1]. Using the old Beijing timezone, the New Moon occurred at 23:53 on the 2nd, so the eighth month began on a different day in the calendars. Hong Kong people (using the traditional calendar) celebrated the Festival on 16 September, but those in China celebrated on 17 September. [2]

The Kuomintang may have begun to number the years of their republic in 1929, regarding 1912 as year 1. When the Communists gained control of mainland China October 1, 1949, they simply continued using the Gregorian calendar, but now numbered the years in the Western manner, beginning with 1949. On both mainland China and Taiwan, the months of the Gregorian calendar are numbered 1-12 just like the months of the traditional calendar.

Characteristics of Chinese Calendar

China has a long history and a lot of traditions. Compared with other countries in the world, it is a typical agricultural country, with a long history of agricultural civilization. And all this, to a great degree, is based on the advanced astronomy and calendar.

The birth of Chinese calendar can be seen as a set of astronomical rules the ancient Chinese summed up for the sake of farming. It took shape after a long time of evolvement. The calendar has two main characteristics:

Firstly, it is closely related with traditional Chinese culture, especially the principles included in the Yi Jing. Secondly, it employs a unique computing method -- the Tian Gan (heavenly stems) and Di Zhi (earthly branches) method.

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