Phenology is a period of time every few days.

The Seventy-two Seasons is a supplement to the calendar used to guide agricultural activities in ancient China. It is compiled according to the geography, climate and some natural scenes of the Yellow River Basin, with five days as the weather, three days as the weather, six days as the weather, four years as the age, and "twenty-four solar terms" * * * 72 days a year.

Each climate corresponds to a phenological phenomenon called "waiting". Among them, the plant climate should be germination, flowering, fruiting, etc. Animals should start vibrating, singing, mating, migrating, etc. Abiotic climate should include initial freezing, thawing and thunder. The time series changes of 72 climaxes reflect the general situation of phenology and climate change in a year.

There should be two types of climaxes: one is biological orgasm, in which animals, such as geese, cicadas and earthworms come out. There are also plants, such as peach blossoms, Pingshisheng, and Henaiden. Another kind of abiotic climate is a natural phenomenon, such as water freezing, thunder, soil wetting and intense heat. , its content is very extensive.

But there are also some mistakes, which are not in line with scientific facts, such as the eagle turning into a dove and the bird turning into a clam when entering the water. And there are some things that don't conform to the meaning of solar terms, such as the cool wind, dew and chilling sound in the dog days before summer. Because the waiting time unit is small (once every five days) and the climate is quite different in different years and regions, it is difficult to be widely used.

Seventy-two waiting for introduction:

The existing "Seventy-two Stages" 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), and there are 72 periods in 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".