In Ancient times, monuments and and temples, in fact entire cities were aligned with the Equinoxes and the Solstices. The sun plays a vital role in the lives of many cultures and was in cases worshiped as a god - the god. Why is this? The question why, has been the basis of many archaeological, anthropological and scientific studies. From ancient artifacts, documents and oral traditions passed down through the centuries all we can do is surmise.
The Equinox's mark the exact balance of light and dark on the planet. With the Spring Equinox being the one to which the most building alignments are associated. The Solstices are the midway points in each cycle. Thus the Summer Solstice has the longest day and shortest night, and the Winter Solstice has the longest night and shortest day. They are roughly the 21st of June and December however the dates do change by a fews days over the years either side of this due to the earths wobble and rotation time around the sun.
Important locations which have been build according to the four celestial points are :-
Chichen Itza in Mexico
Pyramids of Giza (All four corners are precisely aligned with the stars and it was designed in such a way that at noon on the spring equinox it casts no shadow. The north-south axis is aligned to within three-sixtieths of a degree of true north-south, whilst the London based Greenwich Meridian is out by nine-sixtieths. True north can be measured using the equinoxes as the stars appear to stand still.)
Sphinx at Giza (The sphinx gazes due east to where the sun rises on the morning of the spring equinox. During the era of 10,970 to 8,810 BC (approx) it also gazed towards the constellation of Leo which would have been sign at the spring equinox at this time.)
Angkor Wot in Cambodia (The axis of the temple is offset to give a 3 day anticipation of the coming spring equinox alignment. On the morning of the spring equinox, the sun rises up the side of the central structure of the temple and crowns its pinnacle. Recent discoveries show an underground city of roughly 1000 square miles. This was an important Ancient City build on a powerful vortex.)
The Rite of Spring
Vernal equinox occurs on March 20, 2013
What Happens at the Equinox?
Far from being an arbitrary indicator of the changing seasons, March 20 (March 21 in some years) is significant for astronomical reasons. On March 20, 2013, at precisely 7:02 A.M. EDT, the Sun will cross 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.
Equinox Means "Equal Night"
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. A second equinox occurs each year on Sept. 22 or 23; in 2013, it will be on Sept. 22 at 4:44 P.M. EDT. This date will mark the autumnal equinox in the Northern Hemisphere and the vernal equinox in the Southern (vernal denotes "spring").
Reasons for the Seasons
These brief but monumental moments owe their significance to the 23.4 degree tilt of the Earth's axis. Because of the tilt, we receive the Sun's rays most directly in the summer. In the winter, when we are tilted away from the Sun, the rays pass through the atmosphere at a greater slant, bringing lower temperatures. If the Earth rotated on an axis perpendicular to the plane of the Earth's orbit around the Sun, there would be no variation in day lengths or temperatures throughout the year, and we would not have seasons.
Rituals and Traditions
Modern astronomy aside, people have recognized the vernal equinox for thousands of years. There is no shortage of rituals and traditions surrounding the coming of spring. 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. It is also probably no coincidence that 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.