St. Irenaeus was born in Asia Minor around the year 140. It is not known when he came to Gaul. He was a priest of the Church of Lyons during the persecution of 177 when St. Pothinus, first bishop of the city and the first martyr of Lyons, was put to death. Irenaeus succeeded him as bishop and twenty-five years later was martyred in his turn during a fresh persecution. At a time when Gnostic sects threatened to undermine Christianity by a perversion of Christian thought, St. Irenaeus vigorously denounced all heresies and safeguarded unity of belief by laying down the principles of the doctrinal tradition of the Church.

According to the 1962 Missal of Bl. John XXIII the Extraordinary Form of the Roman Rite, the Vigil of Sts. Peter and Paul is observed with a special vigil Mass. Tomorrow is a solemnity, and so observance of Saints Peter and Paul begins with Evening Prayer I in the Liturgy of the Hours this evening. The liturgical day is from midnight to midnight in the Church's observance, except for Sunday and solemnities which begin with the evening of the preceding day. St. Irenaeus feast is celebrated on July 3 in this form of the Roman Rite.

http://www.catholicculture.org/culture/liturgicalyear/calendar/day.cfm?date=2013-06-28

Different saints say different things to us. Some point to the Blessed Virgin Mary, others to some virtue or other in the way they lived and died. St Ireneaus is the saint that tells us to study our catechisms.