"Earth Day" began in:

"Earth Day" began in 1970, marking a significant moment in the environmental movement. The first official Earth Day was celebrated on April 22, 1970, and it aimed to promote awareness and encourage the protection of the environment. The event was organized by U.S. Senator Gaylord Nelson, who sought to bring attention to environmental issues through grassroots efforts and large-scale demonstrations.

The momentum generated by the first Earth Day played a crucial role in the establishment of the Environmental Protection Agency (EPA) and the passing of important environmental legislation, such as the Clean Air Act and the Clean Water Act. By designating a specific day to focus on environmental concerns, Earth Day helped mobilize millions of people, fostering a sense of global responsibility toward the planet.

The other dates listed do not correspond with the inception of Earth Day and instead reflect different periods in the environmental movement. Therefore, 1970 is the pivotal year recognized for starting this annual celebration dedicated to promoting environmental sustainability and awareness.