The autumnal equinox heralds the arrival of fall in the northern hemisphere, and it's just around the corner. Here's what to know.

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.

In Japan, Autumnal Equinox Day is a national holiday. In Japanese, it’s known as Shubun no Hi (秋分の日), according to Coto Japanese Academy. The roots of the celebration are thought to go back to Shintoism and Buddhism.