Earth Day is a day early each year on which events are held worldwide to increase awareness and appreciation of the Earth's natural environment. Earth Day is now coordinated globally by the Earth Day Network, and is celebrated in more than 175 countries every year.
In 2009, the United Nations designated April 22 International Mother Earth Day. Earth Day is planned for April 22 in all years at least through 2015.
Earth Day was first observed in San Francisco (the City of Saint Francis, patron saint of ecology) and other cities on March 21, 1970, the first day of spring in the northern hemisphere. This day was later sanctioned in a Proclamation signed by Secretary General U Thant at the United Nations where it is observed each year.
Many communities celebrate Earth Week, an entire week of activities focused on environmental issues.