What two days of the year on which the daylight hours and nighttime hours are exactly twelve hours long?

The two days of the year when daylight hours and nighttime hours are exactly twelve hours long are the spring equinox, typically around March 20 or 21, and the autumn equinox, around September 22 or 23. On these dates, the sun is positioned directly above the equator, resulting in nearly equal amounts of daytime and nighttime across the globe.