S Irenaeus, God bless him, neatly divides the calendars of the Roman Rite. Those excellent people who follow the 1962 books, whether in the mainstream or in the SSPX, keep S Irenaeus today, July 3. Novus enthusiasts kept it on June 28. But there is a third group; eccentrics like myself, who use the St Lawrence ORDO. In this ORDO, often commended on my blog, the calendar employed is the Roman Calendar as it was before the Pontificate of Pius XII, in 1939. And that calendar has S Irenaeus on ... the Novus Ordo date, of June 28 (where you can say Mass of the Vigil of Ss Peter and Paul with commemoration of S Irenaeus, or of of S Irenaeus with commemoration of the Vigil, and Last Gospel of the Vigil; happily, the Octave of S John Baptist also gets a look in).
Because the 1962 date of S Irenaeus is a very ephemeral phenomenon, designed to get him off the Vigil of the Apostles. Earlier usage had no problem with combining celebrations; but in the early 1960s we were already going down the path of the Enlightenment/Bugnini rigidities, which disallow any sort of combinations and austerely insist that one Mass has one theme - and no more. So Saint and Vigil had to be disentangled. But when the whole old system of vigils was itself abolished, the mandarins in charge of the calendar after the Council had nothing to prevent them from cheerfully bunging S Irenaeus back onto his original date.
So S Irenaeus was on July 3 for less than a decade.
I suspect you discern the direction I am going. The 1962 calendar is neither unchangeable nor, in fact, ideal. Would it be disastrous to revise it gently, so that, at least, where the Novus Ordo calendar is in line with an earlier form of the Roman Calendar, 1962 came into line with the pair of them?
There is, I think, an increasing tendency to realise that 1962 is a problem; rather betwixt and between as a liturgical dispensation. There is greater interest in forms of the post-Tridentine Rite which were unmarked by the fashions of the mid-twentieth century. A year or two ago, speaking at Brompton, Mgr Schmidt cautiously expressed some thoughts like these. Books have been written ... and I know of one very distinguished 'traditionalist' liturgical writer who himself uses a 1620s Breviary. The English Latin Mass Society is - have you noticed? - itself very craftily careful in how it defines the vintage of the liturgy which it supports ... check it out!