In 1969 at a UNESCO Conference in San Francisco, peace activist John McConnell proposed a day to honor the Earth and the concept of peace, to first be observed on March 21, 1970, the first day of spring in the northern hemisphere.

A month later a United States Senator Gaylord Nelson proposed the idea to hold a nationwide environmental teach-in on April 22, 1970. Nelson renamed the event "Earth Day".

More than 20 million people poured out on the streets, and the first Earth Day remains the largest single day protest in human history. The first Earth Day was focused on the United States. In 1990, Denis Hayes, the original national coordinator in 1970, took it international and organized events in 141 nations.

Earth Day is an annual event on April 22 to demonstrate support for environmental protection. First held on April 22, 1970, it now includes a wide range of events coordinated globally by EARTHDAY.ORG (formerly Earth Day Network) including 1 billion people in more than 193 countries. In 2009, the United Nations General Assembly declared April 22 as International Mother Earth Day.

Numerous communities engaged in Earth Day Week actions, an entire week of activities focused on the environmental issues that the world faces. On Earth Day 2020, over 100 million people around the world observed the 50th anniversary in what is being referred to as the largest online mass mobilization in history.

Other Event:

Celebrating the 123rd Anniversary of the American Power Boat Association (April 22, 1903 - April 22, 2026)

According to Wikipedia