April 21, 753 BC: The Roman world was certain of its foundation date for more than 1000 years. The mythical tale, Ab Urbe Condita, formalized by Titus Livius, was based on the struggle of its founding twins: sons to a god, Mars, and a virgin, Rhea Silvia. Archaeological research and historical critics are now convinced of two things: the city is older and the myth is more recent.