The duration of daytime and nighttime on Earth varies depending on the time of year and the observer's location on the planet. These variations occur due to the tilt of Earth's axis and its elliptical orbit around the Sun. On average, a full day on Earth lasts approximately 24 hours, with 12 hours of daylight and 12 hours of darkness. This equal division of day and night is known as the equinox.
However, as you move closer to the Earth's poles, the duration of daylight and nighttime changes significantly throughout the year. Near the equator, the length of day and night remains relatively constant throughout the year, with minor fluctuations. In contrast, closer to the poles, there are substantial differences in daylight and nighttime duration between the seasons.
During the summer solstice, which occurs around June 21st in the Northern Hemisphere and December 21st in the Southern Hemisphere, the days are longest, and the nights are shortest. In the Arctic Circle, for example, the Sun may be above the horizon for 24 hours, resulting in a full day of continuous daylight. Conversely, during the winter solstice, which occurs around December 21st in the Northern Hemisphere and June 21st in the Southern Hemisphere, the opposite happens, and the nights are longest.
To summarize, the length of daytime and nighttime on Earth can vary from a few minutes of daylight or darkness near the poles during certain times of the year to approximately 12 hours of each during the equinoxes.