The Major Events in the Chinese Calendar Reform History
The History of Chinese Lunar Calendar
Chinese calendar combines solar yearly cycle, lunar monthly cycle, and Stem-Branch daily cycle. The cycles of the Sun and the Moon never have a matching point. Ancient Chinese must adjust the calendar every one hundred years. It's very often that every Chinese emperor published a new calendar for the new nation.
Many historical books were burned during the first emperor of China in the Chin Dynasty (221 B.C.). There is no solid evidence of the first Chinese Lunar Calendar. But the Chinese calendar has a Stem-Branch counting system, which is a cycle of 60. The first king of China is the Yellow King 黃帝. According to the historical document, Yellow King used the day of Winter Solstice as the first day of the year in the 子 Rat month. The first Stem-Branch is Wooden Rat. Chinese trace back the Yellow King should found the nation in 2697 B.C.
We have about 365 days a year. A new moon to another new moon takes about 29.5 days. 12 lunar months takes 29.5 X 12 = 354 days. The cycle of the Moon is off the cycle of the Sun 11 days a year. After three years, the cycle of the Moon has an extra 33 days. The lunar calendar needs to add an extra lunar month to match up the cycle of the Sun. The history of the Chinese Lunar Calendar focused on how to add that lunar leap month into the calendar.
The Theory of Chinese Lunar Calendar
The First Day of the Chinese Calendar Year
- 夏 Shiah Dynasty (2205 B.C.) used the 寅 Tiger month as the first month of the year
- 周 Chou Dynasty (1122 B.C.) used the 子 Rat (Winter Solstice) month as the first month of the year
- 殷 Yin Dynasty (1401 B.C.) used the 丑 Cow month as the first month of the year
- 秦 Chin Dynasty (221 B.C.) used the 亥 Pig month as the first month of the year
- 漢 Han (104 B.C.) Dynasty used the 寅 Tiger month as the first month of the year
- 8-22 (A.D.) used the 丑 Cow month as the first month of the year for a short period
Beginning Time of Chinese Lunar and Solar Months
In order to find out the good solution for the Lunar Leap month, ancient Chinese astronomers had been looking for the common cycle of Sun and Moon. They studied the length of lunar and solar months, the length of a day and year, the number of lunar months in a year and so on, then made many changes in the calendar system. For example, in 殷 the Yin Dynasty (1401 B.C.), the Chinese calendar determined a Leap Month by a lunar month without a Sector Point instead of a Center Point. The major changes in the Chinese calendar reform history were the definition of the beginning time of a lunar month and a solar month.
Before 619 A.D., the Chinese used 平朔 Mean Moon times and 平氣 Mean Sun times to determine the Leap Months over one thousand years long.
After 619, during 唐 the Tang Dynasty, the Chinese used 定朔 True Moon times and 平氣 Mean Sun times to assign the Leap Months for about another one thousand years. That means the new moon time is much easier to observe than the sun longitude position in the sky.
After 1645, 清 the Ching Dynasty, the Chinese used 定朔 True Moon times and 定氣 True Sun times to find the Leap Month locations. That's because the Ching Dynasty imported modern astronomical instruments and had the ability to observe precise the Sun and Moon positions in the sky during years.
- The 平朔 Mean Moon time is the length of a lunar month is the average length of lunar months a year.
- The 定朔 True Moon time is the length of a lunar month is the length between two new moons.
- The 平氣 Mean Sun time is the length of a solar month is the average length of solar months in a year.
- The 定氣 True Moon time is the length of a lunar month is the length between two solar Sector Points.
After 清 the Ching Dynasty, China government began to use the Gregorian Calendar instead of the lunar month for daily activities.
The Starting Day of Chinese Calendar Cycle
Many ancient Chinese astronomers in different dynasties kept trying to calculate back and searching for the beginning of the Chinese calendar cycle. The theoretic day of the starting point of Chinese Calendar is that the day must be
- Sun and Moon were on the same position in the sky at midnight, which must be a New Moon Day
- The Day is the Winter Solstice Day
- The Day is a 甲子 Wood Rat Day, the first day of 60 干支 Stem-Branch cycle
They all failed to get a satisfying answer.
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By Master Allen Tsai on January 27, 2023