The Autumnal Equinox is September 23. This marks the official beginning of the fall season in the northern hemisphere when the hours of daylight and nighttime are equal. The northern hemisphere will become increasingly darker with longer nights until December 21, the first day of winter (the Winter Solstice), when daylight hours will begin creeping up again. This is because the Earth’s axis is tilted, so where sunlight hits the planet’s surface varies with our orbit around the Sun.
