Why is there a difference between the solar calendar and the lunar calendar?

Gregorian calendar is also called solar calendar, and lunar calendar is also called lunar calendar.

Historically, the lunar calendar is much earlier than the solar calendar. People first know the periodic influence of the moon on human beings from production and life. For example:

-the female physiological cycle runs according to the moon;

-The tidal cycle is closely related to the moon;

……

So there is the concept of "one month-that is, one month cycle".

At the same time, it is found that the cycle of alternating cold and warm (one year) is not an integer multiple of the moon cycle. Then summed up the 24 solar terms to guide the arrangement of farm work. The cycle of the 24 solar terms is only one year, or one year on average.

It should be said that people have long known that the cycle of alternating cold and warm can be called a year, and the last day of this year is best at the end of the month to sum up the work of this year and look forward to the bumper harvest next year. So there is a distinction between big and small years: when the end of the next year's beginning of spring and the last month of this year is less than 15, the end of this month is designated as the Spring Festival; If there is more than 15 days between the next year's "beginning of spring" and the end of the last month of this year, add one month, and this end is the Spring Festival; Only 12 months in a year is a small year, and 13 months in a year is a big year.

Later, people called the last month with 30 days as the big year, and the last month with only 29 days as the small year. Therefore, the original off-year is called the average year, and the new year is called Runnian (meaning one more month).

The solar calendar is a year in which the earth revolves around the sun. The solar calendar is a one-year cycle that people summarized after Copernicus discovered Heliocentrism.

This is naturally consistent with the cycle of 24 solar terms.

It should be noted that the solar calendar and the lunar calendar have a guiding role in people's life and production, so the coexistence of the two calendars is inevitable and will still exist in the future.