Many westerners question why the Chinese New Year's Day is not a fixed date in the calendar. It's sometimes in January, sometimes in February, how is it determined? Some say that the Chinese New Year's Day is adjusted according to the leap month so that it falls around the Lichun day (first day of spring). 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 cannot be 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 a lunar phase is about 29.5 days. It always has 12 months in a year and about 354 days in a year. Therefore, after 33 years, there will be a one-year difference from the current calendar. Corresponding to 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 lasts about 365.25 days and is called a solar year. The days in a year are determined this way, either 365 days or 366 days. The current standard calendar used in the world is a kind of tai-yang calendar as 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.
Both the pure tai-yang and tai-yin calendars have their advantages and disadvantages, since both the sun and moon are highly important astronomical objects for humans. On one hand, the cycle of the earth rotating the sun correlates with the four seasons and it has a great impact on humanity and the growth of organisms on the earth. On the other hand, modern science has discovered that the lunar phase impacts human physiology and social behavior. Although modern science does not have an explanation of 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.
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 objects in the sky, thus neither of them could be ignored. The ancient Chinese were particular about the unification of heaven and humans. From a different perspective than modern science, they paid extra attention to the movement of planets and their intertwining relations with human society. 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 a fixed period of time, a leap month is added so that the average days in a year is close to a solar year. Moreover, the sun's movement cycle is divided into 24 solar terms with each term being 15 degrees to 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, almost all the Chinese in the world, plus Korea and Vietnam, use the Chinese traditional calendar to calculate the dates for the New Year, Mid-Autumn Festival, Dragon Boat Festival and Qingming Festival. Other countries have also developed a calendar combining yin and yang (lunar and solar) over the course of history, but none have a calendar that exceeded four solar terms. Only the Chinese calendar uniquely and accurately developed the 24 solar terms. In the Yuan Dynasty (1271 – 1368 AD), Guo Shoujing wrote the book Teaching Time and Calendar
, and it calculated the solar year as 365.2425 days. This is the same as the Gregorian Calendar, which is widely used in the world today, but was developed three hundred years earlier.
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. These have a close relationship with the five elements: metal, wood, water, fire, earth. The twelve Earthly Rows correspond to the twelve months. The Chinese calendar uses the month of the winter solstice as the "Zi" month. In the Earthly branches, Zi (first Earthly Row) is water, which indicates that yin is at its peak and starts to decline, and yang strengthens. It is the same concept as calling midnight the Zi time period (2 hours per period) in ancient China.
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 – 2599 BC) built the first calendar. Later, various calendars were set up in different dynasties and the date of the New Year varied. From the time of Emperor Wu of the Han Dynasty (156 – 87 BC) until now, the tradition of setting the Yin (third Earthly Row) month as the first month of a year was kept, so the first month of the year 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 of the year. However, this situation only happens about every 200 years.
There is no reason to connect the Spring Festival with the Chinese New Year. During the late Qing dynasty time when Yuan Shikai (1859-1916 AD) was in power, the Chinese New Year's Day was renamed as the Spring Festival. But the Chinese people didn't accept 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, thus destroying one of China's traditions.