Why is the lunar calendar date different from the Gregorian calendar date in China?

The lunar calendar in our country is the lunar calendar. Is to consider the movement of the sun and the moon at the same time. Among them, 24 solar terms return completely according to the sun. Therefore, the solar calendar date of each solar term is basically certain, while the lunar calendar date is far apart. But the lunar calendar is based on the monthly moon profit and loss. As we all know, the first day is always a new moon, looking forward to the fifteenth.

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.

The lunar calendar is a calendar that takes into account the relationship between the sun, the moon and the earth. The lunar calendar does not consider the movement of the earth around the sun, so the changes of the four seasons have no fixed time in the lunar calendar and cannot reflect the seasons.