135780 Wax 3 1 day never goes bad. What's behind it?

The next sentence of "135780 wax, 3 1 day is not bad" is: "469 winter 30, only February 28, plus one day in leap year".

I say this because there are seven big months, four small months and one flat month in the Gregorian calendar. The first, third, fifth, seventh, eighth, tenth and twelfth (twelfth lunar month) is a big month with 3 1 day. The four abortion months are April, June, September, 1 1 month; The average month is February.

Extended data:

China's traditional calendar: the provisions of the lunar calendar.

The lunar calendar takes the change cycle of the moon phase, that is, the length of the moon is one month, plus the "24 solar terms" of the elephant calendar, and takes the length of the tropical year of the sun as the year. By setting leap months, the average calendar year adapts to the tropic year.

The lunar calendar belongs to a kind of lunar calendar: its years are divided into flat years and leap years. An average year is twelve months; A leap year is thirteen months. A month is divided into a big month and a small month, with 30 days in the big month and 29 days in the small month, and its average calendar month is equal to the full moon. Which month is older and which month is younger in a year is determined by calculation.