Why are birthdays or some China festivals based on the lunar calendar?

The lunar calendar is a lunar calendar, that is, a calendar based on the moon's movement cycle and taking into account the sun's movement cycle.

Twenty-four solar terms are included in this kind of legislation, which is the main basis for farmers. In ancient China, it was a habit of attaching importance to agriculture and building around agricultural production, so festivals were all in accordance with the lunar calendar.

However, solar terms, solar terms. It contains 12 knots and 12 gas. One part is next to the other. For example, in beginning of spring, rain is the air under festivals, fear is festivals, and the vernal equinox is the air.