Calendar
When:
September 23, 2011 @ 3:04 am – 4:04 am
2011-09-23T03:04:00-06:00
2011-09-23T04:04:00-06:00
What's Up!
Non-NOVAC Event

The date (in the northern hemisphere) when night and day are nearly of the same length and Sun crosses the celestial equator (i.e., declination 0) moving southward (in the northern hemisphere).

http://scienceworld.wolfram.com/astronomy/AutumnalEquinox.html