Earth Day is intended to inspire awareness and appreciation for the Earth’s natural environment. Founded by United States Senator Gaylord Nelson, the first Earth Day was an environmental teach-in on April 22, 1970. The first Earth Day was focused on the United States, however an organization launched by Denis Hayes took it international in 1990 and organized events in 141 nations. Earth Day is now coordinated globally by the Earth Day Network, and is celebrated in more than 175 countries every year. April 22 corresponds to spring in the Northern Hemisphere and autumn in the Southern Hemisphere. Numerous communities celebrate Earth Week, an entire week of activities focused on environmental issues. World Environment Day, celebrated on June 5 in a different nation every year, remains the principal United Nations environmental observance.