It was introduced in 1967 by Paul VI, inspired by the encyclical Pacem in Terris of John XXIII and first observed on 1 January 1968.
It was introduced in 1967 by Paul VI, inspired by the encyclical Pacem in Terris of John XXIII and his own encyclical Populorum Progressio. The day was first observed on 1 January 1968.