72 microseasons
Traditional East Asian calendar system dividing the year into 72 five-day periods, each with a poetic name describing seasonal changes. Used in classical literature and almanacs.
The 72 microseasons are a further division of the 24 solar terms into three parts each.
二十四節気 are the 24 solar terms, each about 15 days long. 七十二候 divides each of those into three shorter microseasons of about 5 days.
節気 is a general term for a solar term. 七十二候 is a specific system of 72 microseasons derived from those terms.
From 七十二 (seventy-two) + 候 (season, climate). The system originated in ancient China and was adopted in Japan, where the microseason names were later adapted to better fit the Japanese climate and natural phenomena.