Canonically, Western Rome 'falling' in 476 (end of Antiquity) and the shift of Latin to Greek as the administrative language of the Eastern Roman Empire by the end of the 7th century, following the Arab conquests & the loss of their eastern provinces (end of Late Antiquity). All in all, these are arbitrary pickings. They don't necessarily correspond to major events in reality. More significant than Odoacar deposing the last Western Roman Emperor is, for example, the establishment of the Carolingian Empire, or prior to this the Renovatio Imperii of Justinian and the ensuing Justinian Plague.