Why is there a lunar calendar?

The lunar calendar takes the time for the moon to circle the earth as the benchmark, that is, 29.5 is a month and 354 days a year. The solar calendar is based on the time that the earth goes around the sun once, and one is a little over 365 days. The difference between the two calendars is about 1 1 day, so a leap month is basically a leap of three years. In fact, China used a calendar of Yin and Yang instead of a pure lunar calendar. It is mainly based on the changes of the sun and the moon to formulate agricultural production, so it is called the lunar calendar, which mainly refers to the Central Plains.