Flying direction of geese in rainy season

After the rain passed the solar terms, the geese began to fly back to the north. The solar term of rain lasts 15 days, and the ancients subdivided it into "third class", every 5 days: "the first class rex sacrifices fish; Second, wait for Hongyan to come; Third-class grass sprouted. " In this solar term, otters start fishing and put the fish on the shore, as if they were sacrificing first and then eating; Five days later, the geese began to fly back to the north from the south; In five days, in the "moist and silent" spring rain, the spirit of the sun rises everywhere in the vegetation and begins to sprout. After entering the next solar term, everything recovers and spring comes.