Did you see the bottom where it says the 'motu proprio' is called Piscis Aprilis? In other words the Latin for the French "Poisson d'avril" or "April Fish" meaning "April Fools?" Americans really need to study languages more.

And for a little more trivia: closer to "home" i.e. Rome: Piscis Aprilis would be in Italian "pesce d'aprile", the term that Italians use for April Fools Day. Incidentally, I was told recently that Spaniard equivalent to April Fool's Day is 28th December, the Feast of the Holy Innocents.