The solar and lunar calendars of the perpetual calendar

The calendars used in Chinese history include the solar calendar, the lunar calendar and the lunisolar calendar. The "Blind Year" is the result of a certain "alignment" arrangement of the lunisolar calendar.

The Gregorian calendar may be the earliest calendar used by our ancestors. It is based on the movement of the sun. The ancients believed that the sun orbited the earth, and one revolution was one year. Today we know that it is the period of the earth's revolution around the sun, but the ancients believed the opposite. According to research by scholars, there was also a solar calendar during the Warring States Period. There were ten months in a year, named after the heavenly stems. The thirty-sixth day of each month was divided into thirty days, and the ten days were named after the earthly branches. In this way, in ten months, there are three hundred and sixty days, plus If there are no "waste days" in the last five to six days, there will be 365 or 366 days in a year. In that case, the solar terms are arranged firstly with the "summer solstice" and "winter solstice", and then with the "spring equinox" and "autumn equinox". The seasonal return year is first divided into spring and autumn, and then the four seasons of spring, summer, autumn and winter are divided into Twenty-four solar terms. There are traces of this calendar in the ancient document "Guanzi", and the Torch Festival of the Yi people and southwest ethnic minorities is related to it. The saying "Winter Solstice is the New Year" is still spread among Lingnan folk, which is the remnant of folk memory of this calendar. The ancients indeed used the winter solstice as the New Year's Day.

In addition, during the Spring and Autumn Period and the Warring States Period, the twelve celestial bodies (earthly branches) were used to record the moon, and the twelve celestial overtime system had been adopted as late as the Western Han Dynasty. From the end of the Western Han Dynasty to the present day, stems and branches have been used to mark the year. This is the Ganzhi calendar. It starts with the beginning of spring and the first day of the month. The eldest year is the return year, and one month contains two solar terms. In the Ganzhi calendar, the year, month and day are all determined by the apparent movement of the sun and have nothing to do with the phases of the moon and the moon, so this is a solar calendar.

The lunar calendar is based on the waxing and waning of the moon. The cycle of a synodic month is twenty-nine or thirty days, and the length of a year is only an integral multiple of the month and has nothing to do with the tropical year. The moon has nothing to do with the four seasons of cold and heat. Both the Greek calendar and the Hijri calendar belong to this calendar. In its year, it is impossible to have "Double Spring" or "Blind Year".

The lunisolar calendar is formulated based on the cycles of the sun and moon. A year is divided into twenty-four solar terms according to the movement of the sun, and is divided into months according to the movement of the moon. The twelve small and big moons add up to only 354 or 355 days. Comparing the two, there is a difference of about eleven days. In order to coordinate the two, the ancients adopted the method of "setting up leaps". One year in several years has thirteen months. From the oracle bones of the Shang Dynasty, we can also see the record of "Twelve Months", which is a clear proof of the establishment of leaps. In the last century, scholars reported that the Yao people in the south still kept the name "Thirteenth Month". The current system of "nineteen years and seven leaps" originated quite early. In the history of our country, since the "Spring and Autumn" period, there are calendars of stems and branches that can be checked, which is enough to prove it.

However, placing a leap month does not necessarily mean that there are two "beginnings of spring" in a year, or there is no "beginning of spring". This also involves the issue of "setting it right", that is, taking that month as the first month. Judging from historical records, this "righting" is more complicated:

The Xia Dynasty used Yin month as the first month, which was called Jianyin;

The Shang Dynasty used December as the first month. , Jian Chou;

The Zhou Dynasty used November as the first month, Jian Zi;

The Qin Dynasty used October as the first month, Jian Hai.

When the Han Dynasty was established, it initially inherited the Qin system, thinking that it had gained the virtue of water, and built Hai. Later, under Emperor Wu, after calculation by Luo Xia Hong, it was changed to the lunar calendar, with Yin month as the first month.

Different “corrections” lead to different starting points for the new year. For example, in Jian Yin, the starting point of Yin month is New Year's Day. Although this method has been continuously improved during the two thousand years since the Han Dynasty, it has generally remained unchanged.

In fact, the phenomenon of two "beginning of spring" (also called "two springs") is just a matter of the leap month in the lunar calendar, which exceeds the length of the 24 solar terms in the span of one year. There is absolutely no such phenomenon in the Gregorian calendar, because the Gregorian calendar has 365 or 366 days in a year, which is similar to the length of the 24 solar terms. When there is a leap month in the lunar calendar (that is, there are 13 months), the year is 383 to 384 days long!