Earth Day, celebrated each year on April 22 was initiated by U.S. Senator Gaylord Nelson of Wisconsin in 1970, which grew into the leading annual pro-environment event on the planet meant to foster environment-friendly policies and habits among Earth-dwellers - that means us.

1. The Earth Day idea grew out of concerns about the fallout of overpopulation on Earth and during the late 1960s, "Zero Population Growth" was a big issue as it continues till date.
2. Earth Day is now observed in 175 countries. The nonprofit Earth Day Network co-ordinates Earth Day activities and it claims that Earth Day is now "the largest secular holiday in the world, celebrated by more than a half billion people every year."
3. Many cities, especially in the United States extend the schedule of Earth Day observance events to be an entire week, usually starting on April 16, and ending on Earth Day, April 22.
4. April 22 is also birthday of Vladimir Lenin.
5. Some environmentalists have criticized that now, Earth Day seems to be more show (celebrations) than action.