Autumn Equinox, 23 September: The Year’s Most Even Day, and Why It Is Called “Fen”
23 September 2026 is the autumn equinox. It is called “fen”, the dividing point, because day and night are almost equal on that day, and because it marks autumn halfway through. The character was explained in a Han-dynasty book, and what the ancients did on this day later turned into Mid-Autumn.