63 was the consulship of Marcus Cicero and Gaius Antonius, which a Roman would express in the ablative of time. While counting AUC, from the foundation of the city, was a possibility, it is not one that was actually used by the population of the city. Instead it was essentially a purely literary feature, and one used pretty much exclusively in history and no other kind of literature. Moreover, it was not particularly common among authors in 63, it really caught on during the Principate (by which time the date of the foundation of the city had been more firmly established). Instead, Romans of the late Republic generally counted the years by the consuls