By the numbers

Celestial spin

March 20 (at 8:07 p.m.): The arrival of the vernal equinox this year.

March 21: The official coming of spring in 1903

March 19: When spring will arrive in 2016

23.4 degrees: The tilt of the earth. That tilt, as well as the Earth’s imperfect spin and slightly elliptical orbit around the sun, are the main reasons for the differences each year

Source: http://www.space.com/spacewatch/050318_equinox.html