According to earthday.org:

Each year, Earth Day -- April 22 -- marks the anniversary of what many consider the birth of the modern environmental movement in 1970.

The height of hippie and flower-child culture in the United States, 1970 brought the death of Jimi Hendrix, the last Beatles album, and Simon & Garfunkel’s “Bridge Over Troubled Water”. Protest was the order of the day, but saving the planet was not the cause. War raged in Vietnam, and students nationwide increasingly opposed it.

At the time, Americans were slurping leaded gas through massive V8 sedans. Industry belched out smoke and sludge with little fear of legal consequences or bad press. Air pollution was commonly accepted as the smell of prosperity. “Environment” was a word that appeared more often in spelling bees than on the evening news.  Although mainstream America remained oblivious to environmental concerns, the stage had been set for change by the publication of Rachel Carson's New York Times bestseller Silent Spring in 1962.  The book represented a watershed moment for the modern environmental movement, selling more than 500,000 copies in 24 countries and, up until that moment, more than any other person, Ms. Carson raised public awareness and concern for living organisms, the environment and public health.

Earth Day 1970 capitalized on the emerging consciousness, channeling the energy of the anti-war protest movement and putting environmental concerns front and center.

Where were you (providing you had been born) 4/22/70?