<P> The United Nations Conference on Environment and Development (UNCED), also known as the Rio de Janeiro Earth Summit, the Rio Summit, the Rio Conference, and the Earth Summit (Portuguese: ECO92), was a major United Nations conference held in Rio de Janeiro from 3 to 14 June 1992 . </P> <P> In 2012, the United Nations Conference on Sustainable Development was also held in Rio, and is also commonly called Rio + 20 or Rio Earth Summit 2012 . It was held from 13 to 22 June . </P>

What is united nations conference on environment and development