It happens every March 20 or 21, signaling the return of sunshine, warmer temperatures, blooming flowers, and birds, bees, and butterflies in the Northern Hemisphere. Or, for those Down Under, it heralds autumn’s arrival. But what exactly is the spring equinox?
Is it an astronomical event? A holiday once marked by the ancients? Actually, it’s both. And don’t let the name fool you—just because those above the equator call it the spring equinox, that doesn’t mean it jibes with the meteorological start of the season. The latter is not based on celestial occurrences, but instead the annual temperature cycle and the 12-month calendar. This year, it fell on March 1.