May Day 
In the modern western calendar, summer in the northern hemisphere begins on the June solstice, when the Sun stands farthest north in the sky. But many other cultures reckoned the seasons differently. The June solstice marked not the beginning of summer, but its midpoint. The season began on May Day -- the first day of May.
May Day is one of four cross-quarter days, which come roughly half way between a solstice and an equinox. The best-known cross-quarter days are Halloween on October 31st, and Groundhog Day on February 2nd. The fourth, called Lammas, is on August 1st.
Unlike solstices and equinoxes, which mark precise points in the Sun's north-south motion across the sky, the cross-quarter days are approximations. The half-way point between the March equinox and the June solstice, for example, occurs on the sixth of May, not the first.
May Day celebrations date back thousands of years. There's some evidence, in fact, that Stonehenge -- the great circle of stones in England that served as both astronomical observatory and religious temple -- was built at least in part to commemorate May Day.
More recently, the Irish celebrated the first day of May as Beltaine. It marked the beginning of the "light" half of the year -- the time with more daylight than darkness. It also celebrated the release of the Sun god and Sun maiden from their captivity during the dark days of winter -- days that were vanquished by the first day of May.
Script by Damond Benningfield, Copyright 2010