Far from being an arbitrary indicator of the changing seasons, March 20 is significant for astronomical reasons. Today, at precisely 7:44 a.m. EDT, the Sun crossed directly over the Earth's equator. This moment is known as the vernal equinox in the Northern Hemisphere. For the Southern Hemisphere, this is the moment of the autumnal equinox.
Translated literally, equinox means "equal night." Because the sun is positioned above the equator, day and night are about equal in length all over the world during the equinoxes.
Modern astronomy aside, people have recognized the vernal equinox for thousands of years. Many early peoples celebrated for the basic reason that their food supplies would soon be restored. The date is significant in Christianity because Easter always falls on the first Sunday after the first full moon after the vernal equinox. Early Egyptians built the Great Sphinx so that it points directly toward the rising Sun on the day of the vernal equinox. The first day of spring also marks the beginning of Nowruz, the Persian New Year. The celebration lasts 13 days and is rooted in the 3,000-year-old tradition of Zorastrianism.
:image d:m, memory statue, straus park, nyc