There are places on Earth where the duration of daylight hours is the same all year round - these are areas lying on the equator. In all other regions of the planet, the length of the day ranges from a maximum on the day of the summer solstice (June 22) to a minimum on the day of the winter solstice (December 22). The closer the terrain lies to the equator, the weaker these fluctuations, and vice versa.
The Earth's axis is tilted to the ecliptic, that is, to the plane in which the Sun-Earth system is located, at an angle of approximately 66.6 degrees. If it were not for this tilt, the duration of daylight hours at any point on the Earth would be the same all year round, being determined only by the geographical latitude of the area. But it is precisely because of this tilt of the axis that the northern hemisphere of the planet in the period between the spring and autumn equinox (from March 21 to September 22) faces the Sun for most of the day. The southern hemisphere, respectively, is facing the Sun for less of the day. Therefore, during the period when it is summer in the Northern Hemisphere, in the Southern it is winter. Well, when the Earth, having described a semicircle around the Sun, moves to the opposite point of its orbit, everything changes. Now the Southern Hemisphere is facing the Sun for most of the day, so summer begins there, and winter in the Northern Hemisphere. Accordingly, the length of the day in the Northern Hemisphere is sharply reduced. On the territory of Russia, as well as throughout the Northern Hemisphere, the shortest winter day is December 22. There are vast areas where polar nights occur in winter, that is, the sun does not rise above the horizon at all. This phenomenon is observed in places located north of the so-called Arctic Circle, that is, a latitude of approximately 66.5 degrees. The duration of the polar night is from several days to several months (in areas close to the North Pole). After December 22 - the day of the winter solstice - the duration of daylight hours is steadily increasing. At first, this increase is almost imperceptible, since it is only a few minutes a day. But gradually the daylight hours become significantly longer. And on the day of the vernal equinox (March 21), which is considered the beginning of the astronomical spring, its duration is compared with the duration of the night.
