SPRING BEGINS at 4:58PM EDT on March 20. This is the moment of the vernal equinox, when the Sun is centered on the celestial equator, where traditionally day and night are balanced.
Some know-it-all types like to mention “equilux” instead of “equinox.” This is some newfangled pedantry that presumes to correct the traditional definition of “12 equal hours of day and night” by accounting for twilight and modern precision such as refraction and the size of the Sun’s disc, stating that this would actually occur on some unspecified date besides the equinox. But the fact is refraction is hard to quantify, varies with temperature and local conditions over the globe, and accounting for refraction and the solar disc would cause sunrise and sunset times to vary with latitude. So there would be no single “day” when all of this could occur everywhere around the globe. So let the know-it-all types bask in their smugness while the rest of us just stick with the traditional geometrical definition that has served just fine since the Ancient Greeks. #equinox #vernalequinox
