What year did the US begin celebrating Earth Day on April 22?

I work best on a deadline so I start projects close to their due date.

A.) 1970

A.) 1970

I work on the tasks that I enjoy most first.

B.) 1942

B.) 1942

I work on the tasks that I enjoy most first.

C.) 1975

C.) 1975

I work on the tasks that I enjoy most first.

D.) 1965

D.) 1965