Feast of the Holy Trinity, also called Trinity Sunday, Christian feast in honour of the Trinity, celebrated in Western liturgical churches on the Sunday following Pentecost (the 50th day after Easter). It is known that the feast was celebrated on this day from as early as the 10th century. Celebration of the feast gradually spread in the churches of northern Europe, and in 1334 Pope John XXII approved it for the entire church. In the church year, Anglican and Lutheran churches date the Sundays that follow this feast “after Trinity”; the Roman liturgy dates these Sundays “after Pentecost.” In Eastern Orthodoxy the first day of the three-day Pentecost feast is known as Trinity Sunday.
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