'Antiquity...ended around 476 AD.' inaccurate

If you look up the sources that are provided by the search engine for your quote, you will find that they refer to Classical antiquity. Although there is some confusion in some of the sources, this is to be distinguished from Late antiquity, the two to some extent overlapping. Of course, nothing particularly dramatic happened in 476; I assume that Odoacer simply decided that his authority in Italy no longer required the fig leaf of a domestic Roman puppet, though appearances were kept up by his acknowledging Zeno as emperor of the west as well as the east. Arguably, a more dramatic event happened in the fourth century with the sack of Rome by the Gauls. But kit is obviously right on the basic point. 476 is too early for the beginning of the Middle Ages. Does anyone seriously think of the Roman Emperor Justinian as a "medieval monarch", as opposed to a monarch of late antiquity?