The micro seasons of dahan Like the other solar terms, dahan has its own three micro seasons to describe the natural changes that usually take place during its 15-day period. The first is 鸡乳 jī rǔ, the only micro season named with two characters, and which suggests that hens will start to lay and hatch their eggs. The reason they only begin to do so in dahan is that the inadequate sunlight in winter means their bodies cannot generate enough Vitamin D, calcium, and other necessary nutrients for giving birth, and their ovaries require ultraviolet rays to become active. The second micro season is 征鸟厉疾