Science, Tech, Math › Social Sciences When Was the First Earth Day? When did Earth Day start? Share Flipboard Email Print Chris Bernard/E+/Getty Images Social Sciences Environment Climate Change and Global Warming Green Living Environment Health Pollution Alternative Fuels Psychology Sociology Archaeology Economics Ergonomics Maritime By Larry West Updated March 17, 2017 Earth Day is celebrated annually by millions of people worldwide, but how did Earth Day begin? When was the first Earth Day? This is a trickier question than you might think. There are actually two official Earth Day celebrations every year, and both got their start in the spring of 1970. The First Widespread Earth Day Celebration The Earth Day most often celebrated in the United States—and in many other countries around the world—first took place on April 22, 1970. It was a nationwide teach-in about the environment, dreamed up by U.S. Senator Gaylord Nelson. A Democrat from Wisconsin, Senator Nelson had been instrumental earlier in introducing conservation in John F. Kennedy's presidency. Gaylord Nelson's Earth Day was modeled on the anti-war teach-in demonstrations that Vietnam war protesters had used successfully to educate people about their issues. On the first Earth Day, more than 20 million people turned out at thousands of colleges, universities and communities all across America for an environmental teach-in day, which sparked a global environmental reawakening. More than half a billion people in 175 countries now celebrate Earth Day on April 22. The April 22 date was chosen for its fit within the American college calendar, before end-of-semester exams but when the weather is likely to be relatively pleasant nationwide. Conspiracy theorists relish the fact that April 22 is also the birthday of Vladimir Lenin, seeing in that choice more than the mere coincidence that it is. A Second Claim to "First Earth Day" Yet, it may surprise you to learn that April 22, 1970 was not the first Earth Day. A month earlier, San Francisco Mayor Joseph Alioto had issued the first-ever Earth Day proclamation on March 21, 1970. Mayor Alioto's action was inspired by John McConnell, a San Francisco publisher and peace activist, who a year earlier had attended the 1969 UNESCO Conference on the Environment where he proposed an international holiday focused on environmental stewardship and preservation. McConnell suggested that Earth Day coincide with the March equinox—the first day of spring in the northern hemisphere, March 20 or 21 depending on the year. It is a date filled with all the symbolism associated with spring, including hope and renewal. That is, until one remembers that south of the equator that date signifies the end of summer and the beginning of autumn. About a year later, on February 26, 1971, then-UN Secretary General U Thant supported McConnell's proposal for an annual global Earth Day celebration at the March equinox, and issued a proclamation to make it official. Today, the United Nations rallies with Senator Nelson's plan and every year promotes an April 22nd celebration of what they call Mother Earth Day. Edited by Frederic Beaudry.