Question

On 21st March and 23rd September days and nights are equal all over the world.

Answer 1

On 21 March and 23 September, the Sun shines vertically on the Equator; therefore, all places on the Earth experience equal days and equal nights. On 21 March, the Northern Hemisphere has spring, while the Southern Hemisphere has autumn. On 23 September, ​the Northern Hemisphere has autumn, while the Southern Hemisphere has spring.