Dear Brother Zhongming:
How are you? The Chinese New Year is just around the corner, I wish you the best. In your last letter, you mentioned that the Chinese New Year's Day is not a fixed date in the calendar and you are very curious about this. Actually, many westerners I have met overseas also have the same question: The Chinese New Year is sometimes in January, sometimes in February, how is it determined? I have read an article on the Internet in English by an expert which explains that the Chinese New Year's Day is adjusted according to the leap month so that it falls around the solar seasonal Lichun day (spring beginning day). That's why the Chinese New Year is also called the Spring Festival.
This is a complete misunderstanding. The traditional "Spring Festival" is on the Lichun day and it is a completely different festival than the Chinese New Year. Generally speaking, the Chinese New Year's Day is the second new moon day after the winter solstice (December 21 or 22, the shortest day of the year), except in some special cases. The new moon day is the day in the lunar phase when the moon can not been seen. The traditional Chinese calendar uses the new moon day as the first day of a month. The opposite of new moon is the full moon and the full moon day is normally the 15th or 16th of the month.
Why is the second new moon day after the winter solstice generally the Chinese New Year's Day? We have to start with the introduction of the Chinese calendar.
Many people call the Chinese calendar the lunar calendar. This is a mistake as well. The true lunar calendar only uses the lunar phase in its calculation which is also called the tai-yin calendar. The period of lunar phase is about 29.5 days. The Islam calendar is a tai-yin calendar, which uses the lunar phase to calculate the month. It always has 12 months in a year and about 354 days in a year. Therefore, for total of its 33 years, it has one-year difference with the current calendar. What corresponds with the tai-yin calendar is the tai-yang calendar, also called the solar calendar. Its calculation is based on the cycle of the earth rotating the sun. One cycle is one year, called a circle year, about 365.25 days. So the days in a year are determined this way, 365 days or 366 days. The current widely used calendar in the world is a kind of tai-yang calendar, it is completely based on the cycle of the earth rotating the sun. The months in a year has nothing to do with the lunar phase.
The both tai-yang calendar and tai-yin calendar have their advantages and disadvantages, since both the sun and moon are the most important planets for human beings. On the one hand, the cycle of the earth rotating the sun correlates the four seasons and it has a great impact on humanity and the growth of other beings on the earth. On the other hand, modern science has discovered that the lunar phase impacts human being's physiology and society. Although modern science does not have an explanation on why and how, scientists have confirmed from their observations that women's menstrual cycles, disease incidence rates, crime rates, traffic accident rates and even people's diet changes all relate to lunar phases.
You may have guessed that the Chinese calendar is not a pure lunar calendar or a pure solar calendar, but a combination of both. In ancient China, the tai-yin (moon) and the tai-yang (sun) are the two most observable planets, thus neither of them could be ignored. Ancient Chinese were particular about the unification of heaven and human beings. They paid extra attention to the movement of planets and their relations with human society from a different aspect than does modern science. The Tao culture has influenced China for more than five thousand years, and one of Tao's important concepts is the balance of yin and yang, so the Chinese calendar uses the lunar phase to define the month, and there are 12 months in a year. After some period of time, a leap month is added so that the average days in a year is close to a circle year. Moreover, based on the sun's movement cycle, every 15 degrees is a solar term for a total of 24 solar terms, and they reflect the four seasonal changes. The calculation of a leap month is also according to the solar terms. Therefore, the Chinese calendar contains both yin and yang calendars. Today, in China, Korea and Vietnam, the Chinese calendar is used to calculate the days for the New Year, Mid-Autumn Festival, Dragon Boat Festival and Qingming Festival. In history, other countries have also developed a calendar combining yin and yang (lunar and solar), but their calendar normally just has four solar terms. Only the Chinese calendar accurately developed the 24 solar terms. In the Yuan Dynasty (1271-1368), Guo Shoujing wrote the book Teaching Time and Calendar, and it calculated the circle year as 365.2425 days. This calculation was the same as the Gregorian Calendar which is widely used in the world, but was developed three hundred years later.
So which month does a year begin with? In ancient China, ten Heavenly Columns and twelve Earthly Rows were combined to count year, month, day and time period. The ten Heavenly Columns are Jia, Yi, Bing, Ding, Wu (fourth tune, different with one of the earthly rows Wu, in third tune), Ji, Geng, Xin, Ren, and Gui. The twelve Earthly Rows, Zi, Chou, Yin, Mou, Chen, Si, Wu, Wei, Shen, You, Xu and Hai, correspond to the twelve months. The Chinese calendar uses the month of the winter solstice as the Zi month, since the Heavenly Columns and Earthly Rows have a close relationship with the five elements. For example, in the Heavenly Columns, Jia and Yi are wood, Bing and Ding are fire. So the Ding-Hai year (2007) is the year of fire boar (not golden boar as was widely spread). In the Earthly branches, Zi is water, which indicates that Yin (lunar in first tune, not the third Earthly Row in second tune) is at its peak and starts to decline, and Yang starts to get stronger. On the day of the winter solstice, the night time is the longest among all the days in a year and it starts to get shorter, while the day time is the shortest and starts to get longer. So this day corresponds to Zi. It is the same kind of correspondence as midnight to Zi time period (2 hours per period).
Although the months correspond to the Earthly Rows, the New Year's Day still had to be decided. Five thousand years ago, the Yellow Emperor (2698 BC - 2599 BC) built the first calendar. Later, there were many calendars set up in several dynasties and the New Year's Day was different in these calendars. For example, the Xia calendar set the Yin (third Earthly Row) month as the fist month, the Yin Dynasty calendar set the Chou (second Earthly Row) month as the first month. From the time of Emperor Wu of the Han Dynasty (156 BC 87 BC) until now, the tradition of setting the Yin month as the first month was kept, so the first month is the second month after the month of the winter solstice (Zi month). Therefore, the Chinese New Year's Day is the second new moon day after the winter solstice. There are also exceptions, such as when the leap month happens in the 11th month. However, this situation only happens about every 200 years.
As you can tell, there is no reason to connect the spring festival with the Chinese New Year. During the time when Yuan Shikai (1859-1916) was in power, the Chinese New Year's Day was renamed as Spring Festival. But the Chinese people didn't buy it, and they still celebrated the Chinese New Year in the traditional way. After 1949, the Chinese Communist Party forcefully implemented this among Chinese people and the Spring Festival replaced the Chinese New Year. This is another story.
The Chinese calendar's compiling actually involves many aspects and is far more complicated than what I have talked about here. What I have mentioned here is just a simple introduction. Hope this answers your questions.
Your cousin: Zhenyan