The variation in daylight hours between summer and winter is primarily caused by the tilt of Earth's axis and its orbit around the Sun. This phenomenon is responsible for the changing seasons and the differences in daylight duration throughout the year.
During the summer solstice, which occurs around June 21st in the Northern Hemisphere, the North Pole is tilted towards the Sun, while the South Pole is tilted away from it. This tilt causes the Sun's rays to strike the Northern Hemisphere at a more direct angle, resulting in longer days and shorter nights. The Sun appears to rise earlier, reach higher in the sky, and set later in the evening. Consequently, there is more daylight, and the Sun may remain visible until later in the evening, such as 8 PM.
In contrast, during the winter solstice, which occurs around December 21st in the Northern Hemisphere, the situation is reversed. The North Pole is tilted away from the Sun, while the South Pole is tilted towards it. As a result, the Sun's rays strike the Northern Hemisphere at a more oblique angle, leading to shorter days and longer nights. The Sun rises later, reaches a lower point in the sky, and sets earlier in the afternoon. This is why it may become pitch-black as early as 5 PM during winter months.
It's important to note that the exact timing of sunrise and sunset can also be influenced by factors such as your geographic location within a time zone and local topography. Additionally, the presence of daylight saving time, if observed in a particular region, can further affect the timing of sunrise and sunset.