The Feast of St. Henry is celebrated on July 15th. in the Extraordinary Form of the Roman Calendar, in the Ordinary Form, it is kept on July 13th,, which is apparently the actual date of the Saint's death.
The following is taken from Catholic Online:
"St. Henry, son of Henry, Duke of Bavaria, and of Gisella, daughter of Conrad, King of Burgundy, was born in 972. He received an excellent education under the care of St. Wolfgang, Bishop of Ratisbon. In 995, St. Henry succeeded his father as Duke of Bavaria, and in 1002, upon the death of his cousin, Otho III, he was elected emperor. Firmly anchored upon the great eternal truths, which the practice of meditation kept alive in his heart, he was not elated by this dignity and sought in all things, the greater glory of God. He was most watchful over the welfare of the Church and exerted his zeal for the maintenance of ecclesiastical discipline through the instrumentality of the Bishops. He gained several victories over his enemies, both at home and abroad, but he used these with great moderation and clemency. In 1014, he went to Rome and received the imperial crown at the hands of Pope Benedict VIII. On that occasion he confirmed the donation, made by his predecessors to the Pope, of the sovereignty of Rome and the exarchate of Ravenna. Circumstances several times drove the holy Emperor into war, from which he always came forth victorious. He led an army to the south of Italy against the Saracens and their allies, the Greeks, and drove them from the country. The humility and spirit of justice of the Saint were equal to his zeal for religion. He cast himself at the feet of Herebert, Bishop of Cologne, and begged his pardon for having treated him with coldness, on account of a misunderstanding. He wished to abdicate and retire into a monastery, but yielded to the advice of the Abbot of Verdun, and retained his dignity. Both he and his wife, St. Cunegundes, lived in perpetual chastity, to which they had bound themselves by vow. The Saint made numerous pious foundations, gave liberally to pious institutions and built the Cathedral of Bamberg. His holy death occurred at the castle of Grone, near Halberstad, in 1024. He is the patron saint of the childless, of Dukes, of the handicapped and those rejected by Religious Order."
Prayer for the Holy Roman Emperor (from the Extraordinary Form Liturgy of Good Friday, usually omitted, due to their being no present incumbent):
Oremus et pro Christianissimo imperatore nostro [Nomen] ut Deus et Dominus noster subditas illi faciat omnes barbaras nationes ad nostram perpetuam pacem.
Diaconus: Flectamus genua.
Omnipotens sempiterne Deus, in cujus manu sunt omnium potestates, et omnium jura regnorum: respice ad Romanum benignus imperium; ut gentes, quae in sua feritate confidunt, potentiae tuae dexterae comprimantur. Per Dominum...
Let us pray also for the most Christian Emperor [Name] that the Lord God may reduce to his obedience all barbarous nations for our perpetual peace.
LET US PRAY.
Deacon: Let us kneel.
O almighty and eternal God, in whose hands are all the power and right of kingdoms, graciously look down on the Roman empire that those nations who confide in their own haughtiness and strength, may be reduced by the power of Thy right hand. Through the same Lord…