How is the time point in beginning of spring determined?

The 24 solar terms of the China lunar calendar are divided according to the position of the sun on the ecliptic. When the sun reaches 3 15, it will be beginning of spring. When it reaches this scale accurately, it also represents the official arrival of beginning of spring, so the time will be very accurate.

Beginning of spring moment is a point in time, but it is a period after beginning of spring. In the China lunar calendar, the15th day in beginning of spring is divided into three periods, each lasting 5 days. There is such a name: "The east wind thawed, the second insect stung, and the third fish lost ice", which means that after beginning of spring, the east wind warmed up, the ice and snow began to thaw, and the hibernating insects slowly woke up in the cave five days later.

However, this climate phenomenon is not the same in the whole country, and it should be in some areas from the south of the Yellow River to the north of the Yangtze River. However, China is located in the northern hemisphere. After the arrival of beginning of spring, the national climate will get warmer and the sunshine will get stronger and stronger, so beginning of spring represents that winter has passed and spring has arrived.