Ah, I remember it well. I was teaching earth science in Pomona (actually Diamond Bar) CA when Sen. Gaylord Nelson came up with this bright idea to celebrate an "Earth Day" on April 22, 1970.
Being an environmentalist already, that declaration gave me the impetus to further dedicate my teaching to educating youth in SAVING the planet, not simply learning about it.
I remember making a banner that stated "Every Day is Earth Day". I posted that message every year for the next 30 years. I'd like to think I and the message had an impact on thousands of students. Whether it did or not, I tried.
40 years later, we're still in a fix, globaly. But I've noticed many improvements. Prairie Creek, which flows through my home town, is no longer multi-colored with chemicals and silt. My fellow humans still litter the roadways, but good citizens pick up after them. Progress--slow, but determined.
We've come a long way, baby. Let's keep going.