World Environment Day 

World Environment Day (WED) is celebrated annually on 5 June and is the United Nations' principal vehicle for encouraging awareness and action for the protection of the environment.

Eco Day is June 5, 2023 

Eco Day, Environment Day, or WED (World Environment Day) was first held in 1973, it has been a platform for raising awareness on environmental issues as marine pollution, overpopulation, global warming, sustainable development and wildlife crime. World Environment Day is a global platform for public outreach, with participation from over 143 countries annually. Each year, the program has provided a theme and forum for businesses, non government organizations, communities, governments and celebrities to advocate environmental causes.

World Environment Day was established in 1972 by the United Nations at the Stockholm Conference on the Human Environment ( 5–16 June 1972), that had resulted from discussions on the integration of human interactions and the environment. One year later, in 1973 the first WED was held with the theme "Only One Earth"

Similar but Different from Earth Day