The twenty-four solar terms divide the ecliptic into equal arcs of fifteen degrees, and this one falls at 75 degrees of the sun's apparent longitude. It is a sectional term, a jie, one of the twelve that fall in the odd positions of the twenty-four and open the twelve solar months. The sectional terms and the major terms alternate strictly around the year, so a jie is always followed by a zhong fifteen degrees later.
The system travelled with the Chinese calendar. Japan, Korea and Vietnam all adopted the twenty-four terms and kept their own readings of the same names, and the terms remain in use in each. In 2016 the twenty-four solar terms were inscribed on the UNESCO Representative List of the Intangible Cultural Heritage of Humanity, on the ground that they remain a living framework for agricultural and everyday practice rather than an obsolete scheme.
Mangzhong names the awned grain, the bearded cereals, and marks the point at which they are ready to be harvested and the rice to be transplanted. It is among the most agriculturally specific of the twenty-four names, and it illustrates the limit of the system as well as its use: the terms were fixed against the climate of northern China, so their agricultural instructions were never uniformly applicable across the whole of the country, let alone the countries that later adopted them.