The Solemnity of the Most Sacred Heart of Jesus was approved by Blessed Pope Pius IX in 1856, after being locally celebrated in France since the mid 18th Century. Modern devotions to the Sacred Heart of Jesus were based primarily on the visions of St. Mary Alacoque (1647-1690), however similar devotions can be traced back to European monastic communities in the 11th century.
In 1673, St. Mary Alacoque had a vision of Christ's Heart on the feast of Saint John that was similiar to that of St. Gertrude the Great (1256-1302). In both cases, Jesus permitted them to rest thier heads upon His Heart, and then disclosed to them the wonders of His love.
The devotion to the Sacred Heart focuses on Acts of Reparation for insults and blasphemies against Jesus Christ and his Holy Name. The date of this Solemity remains on the date the Lord himself asked St. Mary Alacoque for it celebrated on; the Friday after the octave of Corpus Christi; 19 days after Penetecost.
The propers for the Solemnity of the Sacred Heart of Jesus, are some of the most beautiful in liturgy; here are a few examples: