According to scienceworld.wolfram.com and solar.physics.montana.edu: The Vernal Eqinox is when night and day are nearly the same length and sun crosses the celestial equator ( the projection of the Earth’s equator onto the sky) moving northward. On the Vernal Equinox the sun rises exactly in the east travels through the sky for 12 hours and sets exactly in the west. On the Equinox this is the motion of the sun through the sky for everyone on earth. Every place on earth experiences a 12-hour day twice a year on the Spring and Fall Equinox.
I think that is so cool and it happened yesterday. It was officially spring at exactly 6:07pm MST. Soon we will be sleeping with the bedroom window open, eating dinner from the garden at 9pm and swimming in the Clark Fork.