Twice a year, the sun doesn’t play favorites. Everyone on Earth is seemingly on equal status – at least when it comes to the amount of light and dark that they get.

So is the autumnal equinox, which marks the end of astronomical summer and the first day of fall in the Northern Hemisphere. The exact time of the fall equinox changes slightly each year. This year, the equinox arrives Sept. 22 at 8:43 a.m. Eastern time.

The official first day of fall, otherwise known as the autumnal equinox, is this weekend in the Northern Hemisphere. According to Encyclopedia Britannica, it is one of only two days, the other being the vernal equinox, when the sun is directly above the Equator, essentially dividing night and day into equal portions.