There are two times of the year when - most places on Earth - periods of daylight and darkness are about equal. September 22 is one of them.

The Autumn Equinox (Sept.22) is the first day of the Season of Autumn in the Northern Hemisphere*. It signals the beginning of a long period of darkness at the North Pole.

Since June 21 (the Northern Hemisphere's Summer Solstice), the Sun has been moving southward, and today it crosses the Equator (the imaginary line around the middle of the Earth). It is an equal distance from the North Pole and the South Pole.

Although the middle of the Sun is even with the Equator, viewed from the North Pole, the top half of it is still peeking above the horizon. The Sun will not fully "set" for another two days, but by September 25th, it will disappear completely and twilight will overtake the Pole. By October 7th, the long Arctic night will have set in. That's when things REALLY get cold!

Elsewhere in the Northern Hemisphere, hours of darkness will exceed the hours of daylight. Check our guide to Arctic Sunrise & Sunset for details.

* NOTE: September 22 is also the first day of the Season of Spring in the Southern Hemisphere, but this is a site about Arctic things, so, like, who cares?