What is the relationship between the 24 solar terms and the calendar?

"Twenty-four solar terms" is an important part of the ancient calendar in China. According to the position change of the sun in a year and the evolution sequence of the ground climate caused by it, the ancients divided the 365th day and the quarter day of a year into 24 segments, and then divided them into 12 months to reflect the four seasons, temperature, phenology and so on. This is the twenty-four solar terms. Every month is divided into two sections, the first section is called "solar terms" and the middle section is called "qi". In order to facilitate memory, people have compiled a ballad: "Spring rains startle spring and clear valleys, summer is full and summer is hot, autumn is cold and frost falls, and winter snow is raining." Twenty-four solar terms are often used in ancient poetry, such as "Yangzhou Slow": "Xi Chun Shen Bing went to Japan and gave it to Weiyang." The solstice in summer is the longest and the solstice in winter is the shortest, so the ancients called the solstice in summer and the solstice in winter, which means the solstice in winter.