World Environment Day

In 1972, the United Nations General Assembly established this observance to raise environmental awareness worldwide. (The event’s June 5 date was chosen to coincide that first year with the start of the 1972 United Nations Conference on the Human Environment, in Stockholm, Sweden.) Each year, a related international event takes place, as well as events in many countries, such as bicycle parades and tree planting.

From: Almanac.com