The 72-hour waiting formula takes 5 days as the waiting time, 3 times as the same, 6 times as the same and 4 times as the age. There are 72 solar terms in a year. Each climate corresponds to a phenological phenomenon, which is called climate response. Among them, the plant climate should be germination, flowering and fruiting.

Animals should start vibrating, singing, mating, migrating, etc. Abiotic climate should include initial freezing, thawing and thunder. The time series changes of 72 climate events reflect the overall situation of climate change in a year.

Seventy-two explanations

Seventy-two periods are compiled according to the signs of natural phenomena such as animals and plants in the Yellow River basin, which are used to explain the changes of solar terms and serve as the basis for agricultural activities in the Yellow River basin.

5 days is a cycle, and 365 days a year (normal year) is 72 cycles. In order to correspond to the twenty-four solar terms, it is stipulated that three periods are one period (qi), with a total of 72 periods a year.

The "weather" of weather should include abiotic and biotic. The former includes "the water begins to dry up", "the east wind thaws", "the rainbow begins to see" and "the ground begins to freeze". The latter includes animals and plants, such as "the swan goose comes", "the tiger begins to make love", "Ping begins to live", "Bitter vegetable show" and "the peach blossom begins to bloom".

Someone made a convenient memory formula for seventy-two waiting periods: "Five days is waiting, three days is waiting, six days is waiting, and four days is old. There are 72 cycles in 24 solar terms in a year. Each climate corresponds to a phenological phenomenon, which is called climate response.