The longitude of the day is the time between sunrise and sunset, when the Sun is visible above the horizon. A solar day is an interval from one sunrise to another. Sunrise and sunset are moments when the Sun crosses the visible horizon line with the upper edge.
The longitude of the day depends on the season and the latitude of the area.
The longitude of the day varies throughout the year, because of the change of the slope relative to the Sun. For example, in the north in summer, the day is longer than in winter, in the south it is vice versa. But at the equator, the longitude of the day is almost unchanged - about 12 hours all year round.
The longitude of the day in different cities is different due to their location: the farther the city is from the equator, the shorter the day there is in winter and the longer in summer. For example, Moscow is located at 55 ° north latitude, St. Petersburg is 59 ° north latitude, and Surgut is even further from the equator, at 61 ° north latitude. On the same day, for example, June 6, the day length in these cities will be different: 17 hours 19 minutes in Moscow, 18 hours 30 minutes in St. Petersburg, and in Surgut the Sun will shine 18 hours 59 minutes. That is, the norther the city is, the longer the summer day is there. In winter, the opposite is true: the norther the city is, the shorter the day is there/
The maximum longitude of the day falls on June 22 or June 21 (in a leap year) in the Northern Hemisphere and on December 22 in the Southern one. This day is also called the summer solstice. In Moscow in this day, the Sun is over the horizon 17 hours 34 minutes.
The shortest day (minimum longitude of the day) in winter is December 22 (21) in the Northern Hemisphere and June 22 in the Southern Hemisphere; it is the winter solstice.
In the days of the spring and autumn equinoxes (March 21 and September 23) everywhere on Earth, the day is slightly longer than the night.