The Feast of the Sacred Heart (properly the Solemnity of the Most Sacred Heart of Jesus) is a solemnity in the liturgical calendar of the Polish National Catholic Church. It falls 19 days after Pentecost, on a Friday.
Devotion to the Sacred Heart of Jesus can be clearly traced back at least to the eleventh century. It marked the spirituality of Saint Bernard of Clairvaux in the twelfth century and of Saint Bonaventure and Saint Gertrude in the thirteenth. The beginnings of a devotion toward the love of God as symbolized by the heart of Jesus are found even in the fathers of the Church, including Origen, Saint Ambrose, Saint Jerome, Saint Augustine of Hippo, Saint Hippolytus of Rome, Saint Irenaeus, Saint Justin Martyr and Saint Cyprian.
But the first liturgical feast of the Sacred Heart was celebrated on 31 August 1670, in the major seminary of Rennes, France, through the efforts of Saint John Eudes. The Mass and Office composed by this saint were adopted elsewhere also, especially in connection with the spread of devotion to the Sacred Heart following on the revelations to Saint Marguerite Marie Alacoqueand Mary of the Divine Heart. A Mass of the Sacred Heart won approval for use in Poland and Portugal in 1765, for Venice, Austria and Spain in 1788 and finally, in 1856 as obligatory for the whole Church.