22 April 1970
Source:
BG E11/999
In 1970, within a short period of time, two International Earth Days were launched. Both days were initiated by US civilians dedicated to the environment and care of our planet. Even today March 21 and April 22 compete with each other for the official title of International Earth Day. March 21 was officially recognized by the United Nations. This poster is from the rival movement of April 22.