With all that's happened on April 22, it's clear that the most celebrated April 22nd is the one that first happened in 1970 and gave us Earth Day ever since. I think that speaks to the power of the ideas behind this day. Of course, as the Library of Congress reminds us, Earth Day is not the first to mark setting aside a day for natural recognition. From the site: "Both Arbor Day and Bird Day were established in the late 1800s to support forestation, conservation, and the appreciation of nature. Native American peoples have long recognized and celebrated in story and song the interdependence of the earth and all her creatures." And, as the slogan says, we can make every day Earth Day.
P.S. - Today also marks AutoblogGreen's first birthday. More on that in a bit.
[Source: Wikipedia, LOC]