What is the "middle qi" in the 24 solar terms?

To put it simply, Zhongqi is an even solar term among the 24 solar terms, and every other solar term in chronological order is Zhongqi. Strictly speaking, this is not a lunar calendar, but a solar calendar that divides a year into twelve solar terms and twelve neutral qi, among which the neutral qi is: rain, vernal equinox, Grain Rain, Xiaoman, summer solstice, summer heat, autumn equinox, first frost, light snow and winter solstice.