Also, the observation of basic astronomical events would appear to have been practised, as many of the monuments have alignments that lend themselves to the solstices.

BBC: Discovering Britain��s prehistoric stone circles

Other responsibilities include overseeing arrangements for summer and winter solstices.

BBC: Stonehenge general manager sought

Notably, every 18.6 years, during the northern lunar standstill, the moonrise is aligned with the sites two rock pinnacles, as well as during the summer and winter solstices, and the fall and spring equinoxes.

WHITEHOUSE: The White House

Although the seasonal equinoxes and solstices seem to divide the year into four equal parts, when you count the days of what we officially call winter, spring, summer and fall, each season is different, says Bing Quock, acting chairman of the Morrison Planetarium at the California Academy of Sciences.

NPR: Not All Seasons Are Created Equal