Who, I will confess, I don't know much of anything about (and I don't recall anything from last May, either-- some other feast took precedence, or perhaps the 18th was the Sunday last year? I never do keep track of how that works). I began to be interested in tomorrow because it the first of the three Rogation days, the days of the Litaniae minores, and I wanted to have it straight in my head how that plays out in the sacred Liturgy. The esteemed Rubricarius says that if only one Mass will be celebrated it's to be Exaudivit but I seem to have vaguely noted that Saint Eugène will be celebrating Protexisti (the Latin with a French version is here; Introibo.fr gives Exaudivit as the Mass), while what Warrington does, I have no guess to make: on the day of the Litaniae maiores, St Mark's Day, they celebrated... I cannot recall which Mass. The old order included three Masses tomorrow (in cathedrals and major churches, anyway): Protexisti with a commemoration of the Rogations, the Rogation procession, then the Rogation Mass Exaudivit; which was the third I have no idea-- Rubricarius probably imagines that to be an obvious thing, which of course it isn't, not to me.
An aside. Dr Eleanor Parker, @clerkofoxford, sent out a lovely translation from the Old English Martyrology for the Rogations along with her own insightful, graceful commentary thereupon this morning, but I gather that since that is a courtesy to subscribers I ought not to share excerpts here. Read her blog, and follow her on Twitter!
Anyway, St Venantius stuck in my head for a bit because his feast actually has three proper hymns (for Vespers, Matins, and Lauds) written in the 17th century. Dom Matthew Britt OSB says that Martyr Dei Venantius is the Vespers hymn and Athleta Christi nobilis the Matins: but the site I use for the Office, Divinumofficium.com, gives Martyr Dei Venantius for Matins. What to do.... am going to read the hymns from Britt. But it would be interesting to know what changed when; Dom Matthew published his The Hymns of the Breviary and Missal in, it looks like, the 1920s; I generally use the 1910 calendar at Divinumofficium. There was a great deal of messing about with the sacred Liturgy after 1910 so who knows.
This is the best I could do...