The time in spring and autumn when the earth has days and nights of equal length is called the

An equinox occurs twice a year when the sun crosses the celestial equator, resulting in approximately equal daylight and nighttime hours everywhere on Earth. This happens around March 21 (vernal/spring equinox) and September 23 (autumnal equinox). The term comes from Latin 'aequinoctium' meaning 'equal night.' Axis is the imaginary line Earth rotates around, and orbit is Earth's path around the sun.