Ab urbe condita — Roman chronological era

Latin for “from the founding of the City,” a Roman system of year numbering tied to the traditional foundation of Rome (commonly dated to 753 BC). Used in ancient historiography and later chronology.

Ab urbe condita is a Latin phrase meaning "from the founding of the City" and denotes a way of counting years from the traditional date of Rome's foundation. The expression is often abbreviated AUC (or A.U.C.) and appears in ancient and later writings as a chronological reference. The name of the system is also the title used by the historian Livy for his monumental history of Rome, Ab Urbe Condita.

The era is conventionally tied to the date proposed by the Roman scholar Marcus Terentius Varro, who placed Rome's foundation in 753 BC. Because ancient authors used a variety of local and political systems for dating events — consular years, regnal years, Olympiads, and indictions — the AUC label was not universally applied in everyday Roman practice, but it became useful for historians trying to align Roman chronology with other dating systems.

Conversion and examples

Converting between AUC and the modern BC/AD system requires knowing the foundational reference. Using Varro's traditional date (AUC 1 = 753 BC) yields simple relations:

AUC = AD year + 753 (for AD years); for example, AD 1 = AUC 754.
AUC = 754 − BC year (for BC years); for example, 753 BC = AUC 1.
There is no year zero in the classical system, so conversions across 1 BC/AD 1 require care.

Different ancient authorities proposed other foundation dates, so historians must check which epoch an author meant. For practical reference, modern scholars commonly adopt Varro's chronology unless another ancient source is specifically invoked.

Usage in literature and inscriptions varied. Some Roman historians and later chroniclers used AUC to present a continuous national chronology; others preferred listing consuls or using regnal years of emperors. The historian Livy used the concept explicitly in his work, which originally ran to many books and was a major source for Rome's early history. Medieval and Renaissance scholars sometimes revived AUC dates when reconciling classical and Christian chronologies.

Notable points to remember:

The literal phrase emphasizes Rome as the point of origin for the era.
Abbreviations and variant Latin forms (for example, "Anno Urbis Conditae") appear in manuscripts and inscriptions.
For further introduction to the term and its historical use see Ab urbe condita.