Why is New Year's Eve gone? It's all because of the moon

“Children, don’t be greedy, the New Year will come after Laba Festival… Stay up all night on New Year’s Eve and walk around the streets on the first and second days.” This familiar nursery rhyme expresses people’s anticipation for the Spring Festival and has also ingrained the perception that New Year’s Eve should be the “standard” of the Spring Festival.

However, from this year to 2029, New Year's Eve will fall on the 29th day of the twelfth lunar month. The continuous absence of New Year's Eve has made many people who are used to equating New Year's Eve with New Year's Eve lament that "without New Year's Eve, the Chinese New Year always feels like something is missing."

Why is the annual New Year’s Eve not always on the last day of the year as the nursery rhymes say?

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"This is related to the unique calculation rules of the lunar calendar in my country." Qi Rui, deputy director of the Beijing Planetarium, said that the lunar month is based on the period of the moon's orbit around the earth and the period of the earth's orbit around the sun. Modern astronomy has accurately calculated that the entire lunar phase change cycle is about 29.5306 days based on the high-precision position model of the moon and the sun. This cycle is defined as a "synodic month", which is a lunar month.

Since the number of days in a month must be expressed as an integer, there is a short month of 29 days and a long month of 30 days. The appearance of long and short months in the lunar calendar is not arranged in intervals of one large and one small or one small and one large, but there may be several consecutive long months or several consecutive short months. Through observation, if the first day of the new moon (the first day) of several consecutive synodic months occurs early, such as in the early morning, there will be consecutive short months. On the contrary, if they all occur in the last few hours of the day, there will be consecutive long months. These need to be determined through precise observation and calculation. Purple Mountain Observatory is responsible for compiling and publishing the lunar calendar for the next year every year, providing services for the public to master the lunar calendar date.

When the twelfth lunar month happens to be a short month, New Year's Eve naturally falls on the 29th day of the twelfth lunar month. Qi Rui said that this "absence" of New Year's Eve occurs about once every 3 to 5 years, and there may even be consecutive "absences". "Since the average length of the 'synodic month' is slightly longer than 29 and a half days, the number of long months each year is slightly more than the number of short months, which also leads to more lunar years with New Year's Eve than without it."

According to statistics, there will be 12 years without New Year's Eve in the next 26 years, that is, until 2050. In addition to the known five consecutive years without New Year's Eve from 2025 to 2029, there will also be three consecutive years without New Year's Eve from 2039 to 2041.

Qi Rui said that the operation rules of the lunar calendar determine that the phenomenon of no New Year's Eve for several consecutive years will occur periodically. But the specific years when it will occur still need to be accurately calculated based on the actual operation of the moon.

"Although there will be no New Year's Eve in the next five years, the traditional customs of New Year's Eve and the entire Spring Festival will not change." Jing Junmei, deputy director of the Institute of Culture of the Beijing Academy of Social Sciences, said that even if New Year's Eve is on the 29th day of the twelfth lunar month, people will still post Spring Festival couplets and stay up on this day. Families will gather together, eat New Year's Eve dinner, watch the Spring Festival Gala, and welcome the arrival of the Lunar New Year together.

In fact, deep in people's hearts, the significance of New Year's Eve does not lie in the day, but in the strong family affection and the atmosphere of family reunion. As netizens said: "As long as you live well, every day is the New Year."

(Reporter Chen Jieshi of Science Popularization Times)

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