Vernal Equinox
The March equinox marks the moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth's equator – from south to north. This happens some time on March 20th for most places on Earth. Equinoxes and solstices are opposite on either side of the equator. The March equinox is also known as the spring vernal (vernal) equinox in the Northern Hemisphere and as the autumnal (fall) equinox in the Southern Hemisphere.

Note: This photo, a 56-minute time-lapse shot, was taken by naturalist Jim McCormac as a celebration of the cold and clear February night skies in Ohio. Temperature was -20°F.