Why did it get dark in China in June+February, 5438?

The sun is in the Tropic of Cancer in summer, the Tropic of Cancer in winter and the equator in spring and summer.

The heat and cold in summer and winter are not determined by the distance between the earth and the sun, because the earth's orbit is almost circular, mainly because of the length of the sun's exposure time.

The autobiographical axis of the earth is not perpendicular to the orbital plane around the sun, and there is an included angle of 66.5 degrees. In this way, there is a period of illumination time at different positions and latitudes in the earth's orbit. In summer, the northern hemisphere has a long illumination time and the southern hemisphere has a short illumination time, so there are summer solstice and winter solstice. Only in the vernal equinox and the autumnal equinox, the illumination time in the northern hemisphere is the same.

You can think of two extremes, the extreme day and night phenomenon in the South Pole and the North Pole.