Prior to the revision of the Breviary instituted by Pope Pius XII, the Octave of Our Holy Father St. Dominic would be celebrated from August 5 till August 11. This is one of the many octaves of the Dominican saints that were casualties of the liturgical revisions of the mid-20th centuries. Not all of the Dominican saints had "solemn" octaves after their feast day, but the major ones like St. Dominic, St. Catherine of Sienna, St. Thomas Aquinas, and St. Peter Martyr did.
Once again, I will restate my bewilderment at the Order giving up some of these wonderful feast days on their calendar, when the calendar was updated in 1961. Even if they wanted to reduce the sanctorale a bit, to make room for new saints and the ferial office, they could still mark the octave of our Holy Father's feast day with a commemoration at Lauds and Vespers.
On August 5, at Pretiosa, we read in the Martyrology for August 6 the commemoration of his death on the actual day that he passed to his eternal reward:
At Bologna, the birthday of St. Dominic, confessor and founder of the Order of Friars Preachers. He was a man of great renown for holiness and learning. Until death he preserved without stain his virginity, and by the singular grace of his merits raised three dead men to life. By his preaching he curbed heresies, and established many persons in a religious and godly manner of life. He died on this day, but his festival, by an ordinance of Pope Paul IV, is celebrated on August 4.
At the very least, the extension of Our Holy Father's solemn feast day is a wonderful way in which to deepen our devotion to him. Every day during the octave, a commemoration was made at Lauds and Vespers using the proper versicle/responsory, Benedictus/Magnificat antiphons from the Dominican Little Office of the Blessed Virgin Mary, and the collect from the feast.
Ad Bened. ant. Benedictus Redemptor omnium, qui saluti providens hominum mundo dedit sanctum Dominicum..
Ad Bened. ant. Blessed be the Redeemer of all, Who, in providing for the salvation of men, gave Saint Dominic to the world.
V. Iustus germinábit sicut lìlium. R. Et florébit in æternum ante Dóminum.
V. The just man will blossom as the lily. R. And he will flourish before the Lord forever.
Deus, qui Ecclésiam tuam beáti Domínici Confessóris tui, Patris nostril, illumináre dignátus es méritis et doctrínis: concéde ut eius intercessióne temporálibus non destituátur auxíliis, et spirituálibus semper profíciat increméntis. Per Dominum nostrum…
O God, you were pleased to enlighten your church with the merits and teaching of the blessed Dominic, your confessor and our father; grant, at his intercession, that she may not be wanting in temporal help, and may always increase in spiritual growth. Through our Lord…
Ad Magnif. ant. Magne Pater sancte Dominice, mortis hora nos tecum suscipe, et hic semper nos pie respice.
Ad Magnif. ant. Great and holy Father Dominic, take us to thyself at the hour of our death and through our life do thou always look kindly upon us.
V. Ora pro nobis, beáte Pater Domínice. R. Ut digni efficiámur promissiónibus Christi.
V. Blessed Father Dominic pray for us. R. That we may be made worthy of the promises of Christ.
At Lauds, if another Confessor’s office occurs, then the versicle/responsory is:
V. Justus ut palma forebit in domo Domini. R. Situt cedrus Libani multplicabitur.
V. The just will flourish like the palm tree in the house of the Lord. R. He shall gow like a Lebanon cedar.
Even if you pray the Liturgy of the Hours, you can still make this commemoration part of your daily Office, by reciting it from August 8 - 15. Traditions like this fed the spiritual lives of so many saints and holy men and women of our Order. They mark out places in time for us to remember those that came before us in this venerable religious order that is now 800 years old. We would do well, in my opinion, to begin to return to some of these liturgical traditions.