The Feast of the Sacred Heart
The principal feast of the devotion — a movable solemnity falling nineteen days after Pentecost.
Why this practice
The Feast of the Sacred Heart was instituted as a universal feast of the Church by Pope Pius IX in 1856, though it had been celebrated locally since the time of St. Margaret Mary. It falls on the Friday after the octave of Corpus Christi — that is, eight days after Corpus Christi, on the day of the week of the Passion.
It is to this devotion what Christmas is to the Incarnation, or Easter to the Resurrection. The other practices of the year are gathered to a point. If a single day is given to the Heart, this is the day.
How to begin
This feast is not one among many. It is the gathering of all that has gone before it — the day when the soul lifts up to His Heart what has been growing in it all year.
— Traditional
A prayer for this practice
O Jesus, on this Thy feast, accept the homage of all that I have tried to do this year for Thy Heart, and pardon what I have failed in. Make this year a true beginning, and the next year deeper still.
Amen.