Assassin's Creed Origins primarily depicts 49 BC.
The game follows Bayek of Siwa and Aya during the final years of Ptolemaic Egypt. Its central events begin in 49 BC, when Julius Caesar arrives in Egypt amid the conflict between Cleopatra and her brother Ptolemy XIII. Bayek and Aya's personal story becomes connected to the formation of the Hidden Ones, the organization that later develops into the Assassin Brotherhood.
Origins presents locations including Alexandria, Memphis, Cyrene, and the Sinai Peninsula. It combines historical figures and political events with fictional characters and the series' science-fiction framing device.
The date can be confused with 44 BC, the year Julius Caesar was assassinated, or 31 BC, the year of the Battle of Actium. Those events belong to the same broad historical period, but Origins begins earlier, chiefly in 49 BC.