Equal Daylight in Arctic and Antarctic: The Equinoxes

Both polar circles experience 12 hours daylight / 12 hours darkness on two dates:

1. March Equinox (~March 20–21): Northern spring / Southern autumn.
2. September Equinox (~September 22–23): Northern autumn / Southern spring.

On these days, the terminator (day-night line) passes through both poles. Everywhere on Earth has ~12h day/night. At the poles, the sun skims the horizon—rising at North Pole (6-month day begins), setting at South Pole (6-month night begins) in March; reverse in September.