When did the twenty-four solar terms begin to be measured by the ancients? What was its function in ancient times?

In the pre-Qin period, the ancient sages of China set four solar terms: midsummer, midsummer, midsummer and winter solstice. Continuously improve and perfect in the future,

By the Qin and Han Dynasties, the 24 solar terms had been completely established. The division of solar terms fully considers the changes of natural phenomena such as seasons, climate and phenology.

Function: To guide agricultural production.

China has always attached great importance to the utilization of farming season and season. In the Eastern Han Dynasty, the Moon Order for Four recorded that farming activities were arranged according to the month and solar terms, while in the Northern Wei Dynasty, the Book of Qi Yao Min made it clear that farming, planting and harvesting were arranged according to solar terms. Later generations also used the twenty-four solar terms as the basis for determining the farming season. With the progress of agricultural production, the content of the 24 solar terms tends to be rich, and the climate changes in different regions are different, so are agricultural activities.