"The vernal equinox and the autumnal equinox are equally divided day and night."

"Equilibration between day and night" means that when the vernal equinox and autumnal equinox arrive every year, day and night are equal in length, that is, day and night are equally divided, and the climate is moderate.

Generally speaking, the day is as long as the night, only twice a year. Therefore, there is a folk saying that "the vernal equinox and the autumnal equinox are equally divided day and night".

When the sun moves to these two points, day and night on the earth are equal. Because on this day, the sun shines directly on the equator, whether in the southern hemisphere or the northern hemisphere, it shines equally on the same area, so the day and night on the earth are equally divided, that is, 12 hour.

Extended data:

The alternation of day and night is produced by the rotation of the earth. Because the earth is not luminous and opaque, at the same time, the sun can only illuminate half of the earth, the illuminated hemisphere is daytime, the unlighted hemisphere is night, and the earth rotates day and night. The dividing line between day and night is called the terminator line.

In the solar terms of the vernal equinox, the sun reaches 0 (above the equator), and the sun just points to the equator. At this time, the terminator line passes through the north and south poles and coincides with the meridian circle of the earth, dividing all latitudes into two parts, half in the day hemisphere and the other half in the night hemisphere, so the day and night in the world are almost equal.