How often is Earth Day observed?

Earth Day is observed annually, on April 22. The date commemorates the first major U.S. Earth Day event, held on April 22, 1970, when environmental teach-ins and demonstrations took place across the country.

The modern observance grew from Senator Gaylord Nelson’s campaign for environmental education after the 1969 Santa Barbara oil spill. Denis Hayes organized the 1970 event, which involved colleges, schools, and communities. In 1990, Earth Day became an international event spanning 141 countries.

A common mix-up is the United Nations’ equinox observance, sometimes called Earth Day and held around March 20. That tradition is distinct from the widely recognized April 22 event. Earth Day is not quarterly or monthly; its principal public observance occurs once each year.

Earth Day has also become a platform for campaigns on climate change, conservation, pollution, recycling, and environmental justice. The 2016 Paris Agreement was opened for signature on Earth Day, linking the annual event with international climate diplomacy.