1, 3, 5, 7, 8, 10, La (that is,1February),

Thirty-one days is never bad.

Winter is 30 days, only February 28th.

Every leap day in four years, February must be added.

Calculation method

Calendar is to calculate the length of years, months and days and the relationship between them. The law of making time sequence is called "calendar". Taking the tropical year as the unit, how many integer months are arranged in a year, how many integer days are arranged in a month, and how to choose the starting point of a year are all called calendars.

The complexity of the calendar problem lies in the fact that the tropical year and the new moon are too fragmented, and their relationship with "day" is not as simple as the relationship between kilometers and meters; Besides, they can't communicate with each other.

Baidu Encyclopedia-Year Month Day