Today that is 20th of June, the longest day of the year. It will happen at 6:34 pm on this very day. It is called the June solstice or the Summer Solstice in the Northern Hemisphere. On this day, the Sun reaches its highest excursion about the celestial equator on the celestial sphere, and it will happen at 6:34 pm this very day.
The same day is called Winter Solstice in the Southern Hemisphere. The two solstices and the equinoxes are directly connected with the seasons of the year. The event usually occurs in the month of June but varies between 20 and 22, which depends on the year and the time zone.
Talking about the technical terms, The Earth revolves around the Sun on a tilted axis may be due to collision with a massive object. In between the March and September, the Northern Hemisphere of the Earth gets more exposed to direct sunlight during a day. “Sun stays a longer period and at the peak level on this particular day rather than the usual”. In contrast to this Southern Hemisphere receives the longest day in the month of December between 21, 22 or 23.
Going deep into the technicalities, the summer solstice occurs when the sun is directly overhead the Tropic of Cancer or above 23.5° north latitude.
The duration of which the sunlight will be available depends on up on the location in the northern hemisphere. Further the north you are located more the time you would get sunlight. This is not the longest day in the entire history because the rotation period of the earth has been gradually slowing over time and the reason for this increase in the period for one rotation is the tidal friction.
It means over very, very extended periods of time the duration of the days has been getting steadily longer. According to the scientists About 4.5 billion years ago, Earth took only 6 hours to complete one rotation and 350 million years ago, and it took 23 hours. At present it’s taking about 24 hours and the days will gradually get longer still.