ReligiousTolerance.org has good information on how Tuesday’s Spring Equinox is celebrated as a sacred time around the globe.

And here are wonderful images of the stones at Cairn T, the ancient Irish burial mound that is aligned like a clock with the Spring Equinox, and built so that the sun near and on March 21st shines brilliantly on a carved ceiling stone. You can look at still images or watch a film of the equinox light illuminating the gray space here. Historians estimate that Cairn T was built around 3200 BC, before the arrival of Celtic tribes.