What do you mean by the fourth and second solstice? Geographical problem ... urgent.

Meteorology talks about "dichotomy"-vernal equinox and autumnal equinox; "Second Solstice"-Solstice in summer and Solstice in winter. These four "solar terms" are the most important of the 24 solar terms.

This dichotomy means that the days are as long as the nights at the vernal equinox and the autumnal equinox.

The second solstice, in the northern hemisphere: summer solstice, the longest day and the shortest night; In the winter solstice, the daytime is the shortest and the research time is the longest.

Followed by beginning of spring, Changchun, beginning of autumn and beginning of winter.