Today (May 8) marks the commemoration of the apparition of Saint Michael the Archangel over Mount Gargano. Here's the story:
And in the year of our Lord three hundred and ninety, was in the same city of Syponte a man which was named Garganus, which, after some books, had taken that name of the mountain, or else the mountain took the name of the man. And he was right rich, and had a great multitude of sheep and beasts, and as they pastured about the sides of the mountains it happed that a bull left the other beasts, and went upon high on the mountain and returned not home again with the other beasts. Then this rich man, the owner, took a great multitude of servants, and did do seek this bull all about, and at the last he was founden on high on the mountain by the entry of a hole or a cave. And then the master was wroth because he had strayed alone from other beasts, and made one of his servants to shoot an arrow at him. And anon the arrow returned with the wind and smote him that had shot it, wherewith they of the city were troubled with this thing, and went to the bishop and inquired of him what was to be done in this thing, that was so wonderful. And then he commanded them to fast three days and to pray unto God.
And when this was done Saint Michael appeared to the bishop, saying: Know ye that this man is so hurt by my will. I am Michael the Archangel, which will that this place be worshipped in earth, and will have it surely kept. And therefore I have proved that I am keeper of this place by the demonstrance and showing of this thing. And then anon the bishop and they of the city went with procession unto that place, and durst not enter into it, but made their prayers withoutforth.
Now then, it seems that the date May 8 does commemorate the day of this vision of Saint Michael, but rather the day on which the Lombards (invoking Saint Michael) conquered the heretical Greeks* at Sipontum on May 8 in AD 663.
Pope Saint Pius V named today the Apparatio Sancti Michaelis.
*At this time, the Byzantine Emperor Heraclius and his Patriarch Cyrus were the masterminds of the monothelite heresy - an evil compromise heresy which attempted to reconcile the monophysite heretics.