Spring has officially arrived — congratulations, everyone.
The vernal equinox of 2013, generally considered the official end of winter, was this year calculated to occur March 20, at 5:02 a.m. MST, according to the Old Farmer's Almanac.
The word equinox is derived from the Latin words meaning "equal night." Days and nights are approximately equal everywhere and the Sun rises and sets due east and west.
As well, today, March 21, is the day when the sun has transitted into the astrological sign of Aries. So today marks the first day of the astrological year.