Earth Day is a name used by two different observances held annually in the (northern) spring, both intended to inspire awareness of and appreciation for the Earth's environment. Earth Day is in the public domain and open to all persons to shape. Some grassroots Earth Day organizers seek to move the date of the observance to the summer solstice, to take advantage of the warm temperatures in the Northern Hemisphere (where most people live) to create greater participation.
The equinoctial Earth Day, also International Earth Day, is celebrated on the vernal equinox to mark the precise moment that spring begins in the Northern Hemisphere and autumn in the Southern Hemisphere. John McConnell first introduced the idea of a global holiday called Earth Day at a UNESCO Conference on the Environment in 1969, the same year that he designed the Earth flag. The first Earth Day proclamation was issued by San Francisco Mayor Joseph Alioto on March 21, 1970.