By the book, the vernal equinox arrived today at 1:14 a.m., marking the official beginning of spring.  According to the Old Farmer's Almanac 2012, this is the earliest that the vernal equinox has occurred in 116 years.

So let's get a little background on what takes place during an equinox, courtesy of www.alamanac.com:

"The word equinox is derived from the Latin words meaning “equal night.” The spring and fall equinoxes are the only dates with equal daylight and dark as the Sun crosses the celestial equator. At the equinoxes, the tilt of Earth relative to the Sun is zero, which means that Earth’s axis neither points toward nor away from the Sun. (However, the tilt of Earth relative to its plane of orbit, called the ecliptic plane, is always about 23.5 degrees.)"