The origins of both lunar and solar calendars are closely related to astronomical observations. The Gregorian calendar is based on the change of direct sunlight points as the Earth orbits the Sun, while the lunar calendar is calculated according to the moon's phases. The moon takes 27.3 days to orbit the Earth, and there is a difference of about 11 days between the lunar and solar calendars each year.

This difference would result in seasonal confusion over five years. To avoid this, the Chinese calendar also incorporates aspects of the solar calendar and introduces the "intercalation method." In a 19-year cycle, there are seven leap months. So this kind of cooperation would better guide daily life, especially in agriculture-led ancient China.

The lunar calendar (moon calendar) was used to keep track of time, besides, its cyclical changes have assumed remarkable emotional sustenance in the Chinese context. While the solar calendar (sun calendar) was used to divide the seasons into spring, summer, autumn, and winter. Each season consists of six solar terms, totaling twenty-four solar terms. This combination reflected Chinese cosmology and philosophy.