February 9th will usher in the Chinese New Year's Eve. Opening the calendar, you will find that 2024 is the last year in the coming years to have a Chinese New Year's Eve. In the five years from 2025 to 2029, there will be no Chinese New Year's Eve. After the 29th day of the Lunar New Year, we will welcome the first day of the Lunar New Year. Where did you go on Chinese New Year's Eve? Why do we occasionally "play and disappear" on Chinese New Year's Eve, and never "be absent" on Chinese New Year's Day? Astronomical science popularization experts will answer your questions. "This situation is related to the calculation rules of the Chinese lunar calendar. In the Chinese lunar calendar, the lunar month is mainly formulated according to the cycle of the moon's waxing and waning changes." Wang Kechao, director of science popularization at the Zijinshan Observatory of the Chinese Academy of Sciences, said that when the moon rotates around the earth, the moon shows different looks from the earth. When the geocentric ecliptic of the moon and the sun is equal, the moon cannot be seen on Earth. At this time, the moon is called Shuo, and the day is called Shuo. It is the initial day of each lunar month and is called the first day of the lunar calendar. Therefore, the first day of the lunar month will appear. Wang Kechao introduced that the interval from one new moon to the next is one month in the lunar calendar, known as Shuo Wang Yue, with an average length of 29.53 days. In fact, the length of Shuo Wangyue is not fixed, it is over 29 days. The shortest time in this century is 29.27 days, and the longest is 29.82 days. Counting by rounding, the lunar month is divided into large and small months, with the former having 30 days and the latter having 29 days. If the twelfth lunar month coincides with the small lunar month, the Chinese New Year's Eve will be absent. The arrangement of lunar months depends on the actual lunar phase, and the arrangement of major and minor months is different from that of Gregorian months. Overall, the proportion of spacing between the two is higher, and sometimes there may be situations where there are two consecutive months or two consecutive months. "According to long-term statistics, the proportion of those who have a year's Eve is slightly higher, and it is normal to not have a year's Eve for five consecutive years, but it is relatively rare," said Wang Kechao. "The solar calendar is a calendar based on the cycle of the Earth's orbit around the sun, while the lunar calendar is based on the cycle of changes in the phases of the moon. The lunar calendar, which has been used in China since ancient times, takes into account the cycle of changes in the moon's roundness and the length of the tropical year. It is a combination of yin and yang calendars, showcasing the ancient wisdom of the ancients." Wang Kechao said. Whether it's the 29th or 30th of the Lunar New Year, the New Year's Eve that connects with the beginning of the new year has always been present. On New Year's Eve, people gather with their families to bid farewell to the old year and welcome the new year, welcoming a brand new and wonderful new year together. (Lai Xin She)