Why is it 5:30 pm in india when it is 12:00 afternoon in london ?

If the Earth were not tilted on its axis, all places on the planet would experience equal day and night throughout the year. Similarly, if the Earth did not revolve around the Sun, one hemisphere would always have longer days and shorter nights, while the other would experience longer nights and shorter days. However, due to the Earth’s axial tilt and its revolution around the Sun, there is a noticeable difference in the length of day and night across different seasons in almost all parts of the world—except the equator.

On the equator, day and night are always equal. This is because the circle of illumination (the boundary between the day and night sides of the Earth) always divides the equator into two equal halves. As a result, each half of the equator receives 12 hours of sunlight at any given time of the year.

From March 21 to September 23, the Northern Hemisphere receives sunlight for 12 hours or more each day, making the days longer and nights shorter. The closer we move towards the North Pole, the longer the duration of daylight becomes. 

At the North Pole, the sun remains visible for approximately six months straight. Similarly, from September 23 to March 21, the Southern Hemisphere receives more than 12 hours of sunlight daily. Moving closer to the South Pole, the duration of the day also increases—leading to six months of continuous daylight at the South Pole, followed by six months of night.

This variation in day and night is due to the Earth’s two types of motion: rotation on its axis and revolution around the Sun. Because of these combined movements, the Earth’s position relative to the Sun keeps changing throughout the year. These changes create four key positions during its orbit, resulting in different seasons and varying lengths of day and night across the globe.