Spring is one of the four temperate seasons, falling between winter and summer. While the calendar marks its official start, the meaning of spring is far richer: it is universally understood as the planet’s great "reset button." 1. The Scientific Meaning: Tilt, Light, and Life Scientifically, spring begins on the vernal equinox (around March 20 in the Northern Hemisphere, September 22 in the Southern). On this day, the Earth’s axis is tilted neither toward nor away from the sun, giving nearly equal day and night worldwide.