"Today, it's the twenty-third day of the waxing moon
Many places call it, Little Year
Although the dates of the "Little Year" are slightly different in different places, the 23rd lunar month in the north and the 24th lunar month in the south, the same is that after the small year, it will enter the countdown to the Spring Festival! I believe that everyone is looking forward to a hearty Chinese New Year's Eve meal at the "Chinese New Year's Eve". We have habitually called Chinese New Year's Eve "Chinese New Year's Eve", but have you noticed that this year there is no "Chinese New Year's Eve", only "year twenty-nine"?
ask
Chinese New Year's Eve is gone, what's going on?
In fact, this is all due to the "too reasonable" of our lunar calendar.
Calendar
1
The most commonly used in our lives now is the "solar calendar", in fact, more precisely the Gregorian calendar, or gregorian calendar. For example, New Year's Day January 1, Labor Day May 1, National Day October 1, etc., these festivals use the Gregorian calendar. The Gregorian calendar is based on the Earth's cycle of rotation, the year of regression, with an average of 365.2422 days a year.
Lunar
2
The lunar calendar is a luni-yang calendar, and its month length is determined by reference to the apparent motion of the moon, the cycle of moon phase changes. The moon is "yin and sunny" A reincarnation is called synodic moon, the new moon is synodic, and the full moon is lookout, hence the name. The average length of a synodic month is 29.5306 days (29 days, 12 hours and 44 minutes). Therefore, the number of days in the lunar month is either 30 days or 29 days, so the folk have the saying that "the big month has 30 days and the small month has 29 days". However, the arrangement of the big moon and the small moon is not arranged in a regular manner, one large and one small, but completely determined by the moon phase.
We often say that "the lunar calendar is a traditional Chinese calendar with a history of thousands of years", but this statement is not accurate. Chinese culture has a long history, there are more than a hundred calendars that have appeared in thousands of years, and the lunar calendar is only the calendar currently used, but it inherits the ancient calendar such as the Xia calendar on the big principles and algorithms. The compilation of the lunar calendar stipulates that the first day of each month, that is, the "first day of the first year", is determined by the time when "Shuo" appears, and this principle is called "Ding Shuo Method".
Take one
example
The past Shuo occurred at 2:33 on January 3, 2022, so January 3 was determined as the first day of the first month of the twelfth month of the lunar calendar; the next Shuo occurred at 13:46 on February 1, 2022, so February 1 was determined as the first day of the first lunar month. In this way, the total number of december in this lunar calendar is 29 days.
If, just past one Shuo occurred 3 hours earlier, that is, at 23:33 on January 2, 2022 (note that it is if), then the first day of the first month of the lunar calendar will be January 2; and the next Shuo will not change, it is still 13:46 on February 1, 2022, that is, the first day of the first lunar month is still February 1, so that the lunar month of December will have 30 days, is this not Chinese New Year's Eve?
The last time the Chinese New Year's Eve was on February 7, 2016, and after this year, the next year was Chinese New Year's Eve, January 28, 2025. Not only that, from 2025 to 2029, the "Chinese New Year's Eve" will be absent for 5 consecutive years.
Is there a law in between?
There are generally regularities, but in parts, the laws do not seem to be very strong.
That's because the size of the moon is not small compared to the earth it orbits around, so the orbit of the moon is not simple, it is constantly swinging, as if a very complex "waltz" is jumping between the earth and the moon. A synodic month cycle averages 29.5306 days, but it is only average, and does not mean that each month is 29.5306 days. This also causes the length of the lunar year to be 354 days, or it may be 355 days, which is not fixed (the probability of 354 days is higher).
If you don't understand, imagine the extreme situation: if Shuo occurs at 23:59, the number of days in the lunar month will be one day less; if Shuo occurs at 0:01, there will be one more day. It is no exaggeration to say that a difference of one or two minutes can determine whether the Chinese New Year's Eve is "thirty" or "twenty-nine".
The lunar calendar is so "reasonable", everything is left to nature to decide!
Author: Shi Wei (Director of Network Science Popularization Department of Shanghai Planetarium Exhibition and Education Center, Deputy Secretary-General of Shanghai Astronomical Society)
Edit: Mu Nan
Audit: Narcissus