During an equinox, places around the globe experience nearly equal amounts of daytime and nighttime. The second occurrence this year happens on Sunday.

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.