Sun Day (May 3, 1978) was designated by United States President Jimmy Carter, specifically devoted to advocacy for solar power, following a joint resolution by Congress, H.J.Res. 715 becoming Pub.L. 95–253 It was modeled on the highly successful Earth Day of April 22, 1970. It was the idea of Denis Hayes, who also coordinated Earth Day in 1970.
Sun Day Wikipedia
While President Carter flew to Denver to visit a solar power research institute, others gathered in Cadillac Mountain in Maine where the sun's ray allegedly first touch the United States (although not at the time of the year). A crowd gathered at UN Plaza in New York City listened to speeches by people such as movie star Robert Redford, who reminded them that the sun "can't be embargoed by any foreign nation". At the Lincoln Memorial in Washington, DC, environmental activist Barry Commoner opined to a group of 500 people that solar power was an issue as pivotal as slavery and that "If Mr. Carter and [Energy Secretary] Schlesinger won't talk about solar energy, it's time that we did." and that solar power was the "... one solution to the economic problems of the United States"
Events were planned in twenty-two countries around the world.