when day and night are equal
when day and night are equal The day and night are equal when we experience what is known as an equinox. An equinox occurs twice a year, around March 20th/21st and September 22nd/23rd, when the tilt of the Earth's axis is neither tilted away from nor towards the sun. This means that the length of day and night are approximately equal all over the world. During the March equinox, the sun moves from south to north of the celestial equator, while during the September equinox, the sun moves from north to south of the celestial equator. The equinoxes mark the transition between the seasons, with the March equinox marking the start of spring in the Northern Hemisphere and the start of autumn in the Southern Hemisphere, and the September equinox marking the start of autumn in the Northern Hemisphere and the start of spring in the Southern Hemisphere.