‘Earth Day is devoted to the harmony of nature … offends no historical calendar, yet transcends them all.’ These words of the famous anthropologist Margaret Mead apply precisely to the equinox. She, with others, chose this fixed event in the calendar to be the first Earth Day in 1969, fifty three years ago. The spring equinox is a natural Earth Day, with a host of advantages built in. Not only that, it has a twin on the other side of the year: the autumnal equinox.
