Equinox Arrives September 22nd

For those of us already seeing blushing foliage or feeling a chill in the air, it might seem as though autumn has already arrived. But astronomically speaking, fall officially comes to Earth's Northern Hemisphere at 20:44 Universal Time on Sunday, September 22, 2013. At that moment, the Sun's path crosses Earth's equator heading south, an event called the autumnal equinox.

http://www.skyandtelescope.com/observing/highlights/Equinox-b-224270151.html