You can make all sorts of arguments for using what is, to most people, a cryptic format useful for sorting data files into order, but not for imparting information to humans -- which is the ultimate goal here. I see no reason to make an estimated 70% of my visitors confused as to when an event is planned to take place simply because W3C standards are more important to me than getting my message across simply and effectively.
I get hits from people doing Google searches like "How do I order valium online?" and "Where can I find a hotel in Berlin?" People who can't tell the difference between Google and Ask Jeeves are not going to want to spend time puzzling over weird dates.
You see, the reason the W3C, in its infinite wisdom, decided that YYYY-MM-DD is to be the only correct format allowed (if indeed that's what the W3C really meant by that) is because they are technically-minded people used to working with data which has to be presented in machine-readable format. YYYY-MM-DD is machine-readable. I need human-readable dates. The W3C are not always correct, and this is one instance where I feel they've got it wrong.
They've made the classic error of assuming everyone thinks like computer technicians. I design websites. I need to think like vicars, housewives and schoolteachers.
I did say "most" European languages. But you spelt the Italian wrong: it's iuglio, and I and J are actually variants of the same letter (and the G is silent but just makes the L sound "liquid"). Even Russian has iul' (although written in Cyrillic).