How did the ancients determine the four seasons through the sun, the moon and the stars?

The stars move and the seasons change, just as the ancient folk song of China sang: the handle of the barrel points to the east, and the world is spring; Guide to barrel handle, it's summer in the world; Bucket handle refers to the west, and the world is autumn; The barrel handle refers to the north, and it is winter all over the world. The Big Dipper moves round and round in the sky, and the time to complete a circular motion is set at one year. The ancients defined him as a solar term every 15 degrees, so there were 24 solar terms in a year. From generation to generation, China people sow, cultivate, harvest in autumn and store in winter according to the changing laws of different solar terms. In the process of observing the changes in the sky for a long time, our ancestors saw a group of seven stars in the sky, namely the "Big Dipper". If you connect them with an imaginary line, it is like a spoon used in people's lives, like a bucket used to measure rice in ancient times. The first four stars are the barrel body, and the last three stars are the barrel handle. Whenever the handle of this bucket points to the east, the sun can point directly to the equator. The ancients designated this time as the vernal equinox. At this time, everything began to revive and the earth showed great vitality. Whenever the barrel handle points due south, the direct sunlight will cross the equator and reach the Tropic of Cancer. China is sunny, and the ancients designated it as the summer solstice. At this time, plants get enough sunlight, and their photosynthesis is the best and they grow the fastest. Whenever the handle of the bucket points due west, the sun will return to the equator. At this time, the plants are mature and full of fruits, waiting for harvest. The ancients designated this time as the autumnal equinox. Whenever the barrel handle points due north, the direct sunlight deviates from the equator and turns to the tropic of Capricorn. At this time, the inclination of the sun is the largest, and most plants on the earth have begun to hibernate. The ancients designated this time as the winter solstice.