What happened to Run February?
Leap February, that is, the lunar calendar has two February in a year, and the second February is leap February. The frequency of leap February is second only to leap March, and the frequency of leap February is moderate around 2 1 century, generally once every 19 years (such as 2004 and 2023). Since then, the frequency of leap February has gradually decreased, becoming a rare leap month.
Every century in the 25th-28th century has a leap February, but there is no leap February in the 29th-30th century, the 36th-38th century and the 40th-44th century. Spring Festival and Dragon Head Festival are the earliest, and the latest year of Shangsi Festival is usually in February. March 22nd, 2023 is the first day of February in the year of Guimao Rabbit.
cause
There are two calendars in most parts of China: one is the solar calendar, and the other is the lunar calendar (also called the summer calendar). The solar calendar, also called the solar calendar, is based on the tropical year. Because the length of the tropic year is equal to 365.2422 average solar days (that is, 365 days, 5 hours, 48 minutes and 46 seconds), it is not a whole day. So the solar calendar takes 365 days as the average year, that is, the "average year".
In order to clear the gap between it and the actual tropic year, the Gregorian calendar adds 97 days in 400 years, or adds one day in February every four years. This is a leap year of the solar calendar, and it is also the "leap February" of the solar calendar.
Lunar calendar is different. In fact, it is a kind of "yin and yang combined calendar" with the same calendar month as the lunar calendar and similar calendar years. It is based on the moon's profit and loss cycle as the calendar month, and also needs to consider the annual solar terms. Generally speaking, the moon's profit and loss period is 29.53 days (that is, 29 days 12 hours, 44 minutes and 2.9 seconds), which is called a "moonshine".
There are 30 days in the big moon and 29 days in the small moon, so a year is 12 months ***354 days. Lunar months have no seasonal significance. Thus, 12 lunar months constitute a lunar year, with a length of 29.5306× 12=354.3672 days, which is 0.9 1 day less than the tropical year (365.2422).
The difference between solar calendar year and year 10.875 days. Only after 17 years, the date of the lunar calendar will be reversed in the same season. For example, one year's New Year was spent in the snow, 17 years later, it will be a New Year's Eve.
Using such a calendar naturally cannot meet the needs of agricultural production. Therefore, the lunar calendar in China has been in parallel with the 24 solar terms since the Qin and Han Dynasties, and the 24 solar terms are used to guide agricultural production.
In order to make the seasons of the lunar calendar and the solar calendar coincide, our ancestors used the method of "adding leap months" to "adjust the surplus and adjust the deficit" and set up seven leap months in 19, because the total number of days in the tropical year of 19 is basically equal to the total number of days in the normal year plus seven leap months in 19.
Therefore, the lunar calendar stipulates a leap month every two or three years. In the year with leap month, the lunar calendar is 13 months, accounting for 383.8978 days.
Through long-term practice, our ancestors divided a year into 24 solar terms, which were placed in 12 months, and each month had two fixed solar terms: the former was called "solar term" and the latter was called "neutral gas". For example, when it rains in beginning of spring and the first month, the former is solar terms and the latter is neutral. Solar terms and neutral gas are alternately arranged in monthly order.
The average interval between two adjacent solar terms and neutral gas is 30.5 days. However, a month in the lunar calendar (the first month of the lunar calendar) has an average of only 29.5 days. In this way, next month's solar terms or gas will be delayed by one or two days compared with the previous month's solar terms or gas. At a certain time, "Zhongqi" was not in the middle of the month, and then moved to the end of the month.
There will be only one "solar term" next month, and there will be no "neutral gas". Therefore, the lunar calendar stipulates that any month with only solar terms and no neutral atmosphere cannot be independent as a month, but can only be regarded as a subsidiary month (sub-month)-leap month.
Leap February appears because the month after February of the lunar calendar only has the solar term "Qingming", and the neutral "Grain Rain" after Qingming falls to the next month. Therefore, the month without neutral gas appears after February. Therefore, the neutral month after February is named "leap February" after February, which is the reason for leap February.