Since the time of Pius XI’s Quas primas in 1925, the following was to be recited on the Feast of Christ the King, which in the traditional calendar falls on the last Sunday of October. In the new-fangled calendar it is the last Sunday of the liturgical year.
There’s nothing wrong with saying this prayer on other days!
Act of Consecration of the Human Race to the Sacred Heart of Jesus
Most Sweet Jesus, Redeemer of the human race, look down upon us humbly prostrate before Thine altar. We are Thine, and Thine we wish to be; but to be more surely united to Thee, behold each one of us freely consecrates ourselves today to Thy Most Sacred Heart.
Many indeed have never known Thee; Many too, despising Thy precepts, have rejected Thee. Have mercy on them all, most merciful Jesus, and draw them to Thy Sacred Heart. Be Thou King, O Lord, not only of the faithful children, who have never forsaken Thee, but also of the prodigal children, who have abandoned Thee; Grant that they may quickly return to their Father’s house lest they die of wretchedness and hunger.
Be Thou King of those who are deceived by erroneous opinions, or whom discord keeps aloof, and call them back to the harbor of truth and unity of faith, so that there may be but one flock and one Shepherd.
Be Thou King of all those who are still involved in the darkness of idolatry or of Islamism, and refuse not to draw them into the light and kingdom of God. Turn Thine eyes of mercy towards the children of the race, once Thy chosen people: of old they called down upon themselves the Blood of the Savior; may it now descend upon them a laver of redemption and of life.
Grant, O Lord, to Thy Church assurance of freedom and immunity from harm; give peace and order to all nations, and make the earth resound from pole to pole with one cry; praise to the Divine Heart that wrought our salvation; To it be glory and honor forever.