Hooray! It's spring! On this day, March 20, 2012, the day and night are almost equally long as the sun passes over the equator in what's known as the vernal equinox.
The season of rebirth has been welcomed by Indigenous Peoples since time immemorial. From the ancient Pueblo of Chaco Canyon, to the Maya in what is today Mexico, the advent of spring and the planting season has been heralded for millennia. On this date the night and day are about equal in length. As National Geographic reported, "winter officially ended at 1:14 a.m. ET on Tuesday, March 20, 2012."
However, although night and day are roughly the same length, it's not completely even.
"The true days of day-night equality always fall before the vernal equinox and after the autumnal, or fall, equinox, according to Geoff Chester, a public affairs specialist with the U.S. Naval Observatory in Washington, D.C.," reported National Geographic. "By the time the center of the sun passes over the Equator—the official definition of equinox—the day will be slightly longer than the night everywhere on Earth. The difference is a matter of geometry, atmosphere, and language."
The ancient Maya kept assiduous track of celestial events, and built vast structures to keep track of them. Chichén-Itzá is among the most famous of those, with a pyramid positioned specifically to give the appearance of a snake slithering down the stairs. Even to this day, it is considered a mystical event, drawing thousands. And it does not disappoint.
The ancient Pueblo of Chaco Canyon were proficient in astronomy. This computer-animated video from IRC, a tech think tank, shows just what the Pueblo were capable of oh so many years ago. The famous Mayan ruins at Chichén-Itzá and Dzibilchaltún draw thousands annually to view the sun's antics. Here they are in action.