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

It should be the legendary Yao and Shun period. Yao Dian in Shangshu records that when Emperor Yao was legendary, he "respected the sky as the sun, the moon and the stars, and respected people as the sky". The specific observation methods and results are as follows: "The stars in the sun are in Yin Zhongchun", "The sun is always sparking in midsummer", "The stars at night are empty, in Yin Zhongqiu" and "The stars in the sun are short, in midsummer", that is, observing the four stars of birds, fire, emptiness and dragons in the south at dusk. According to calculations, this is the actual astronomical phenomenon in about 2000 BC. From the above records, we can infer that people use primitive standards to observe the stars in the southern transit to determine the seasons.