Is it ensure, insure, or assure?
a day's observance of the need to protect the Earth's environment, in many countries on April 22
The first Earth Day was organized in 1970 to promote the ideas of ecology, encourage respect for life on earth, and highlight growing concern over pollution of the soil, air, and water.
as an annual ecological awareness event on April 22, dates to 1970; the idea and the name formed in 1969.
annual celebration honouring the achievements of the environmental movement and raising awareness of the importance of long-term ecological sustainability. Earth Day is celebrated in the United States on April 22; throughout the rest of the world it is celebrated on either April 22 or the day the vernal equinox occurs.