1 BC in the context of "AD"

Ab urbe condita (Latin: [ab ˈʊrbɛ ˈkɔndɪtaː]; 'from the founding of the City'), or anno urbis conditae (Latin: [ˈannoː ˈʊrbɪs ˈkɔndɪtae̯]; 'in the year since the city's founding'), abbreviated as AUC or AVC, expresses a date in years since 753 BC, the traditional founding of Rome. It is an expression used in antiquity and by classical historians to refer to a given year in Ancient Rome. In reference to the traditional year of the foundation of Rome, the year 1 BC would be written AUC 753, whereas AD 1 would be AUC 754. The foundation of the Roman Empire in 27 BC would be AUC 727. The current year AD 2025 would be AUC 2778.

Usage of the term was more common during the Renaissance, when editors sometimes added AUC to Roman manuscripts they published, giving the false impression that the convention was commonly used in antiquity. In reality, the dominant method of identifying years in Roman times was to name the two consuls who held office that year. In late antiquity, regnal years were also in use, as in Roman Egypt during the Diocletian era after AD 293, and in the Byzantine Empire from AD 537, following a decree by Justinian.

The terms anno Domini (AD) and before Christ (BC) are used when designating years in the Gregorian and Julian calendars. The term anno Domini is Medieval Latin and means "in the year of the Lord" but is often presented using "our Lord" instead of "the Lord", taken from the full original phrase "anno Domini nostri Jesu Christi", which translates to "in the year of our Lord Jesus Christ". The form "BC" is specific to English, and equivalent abbreviations are used in other languages: the Latin form, rarely used in English, is ante Christum natum (ACN) or ante Christum (AC).

This calendar era takes as its epoch the traditionally reckoned year of the conception or birth of Jesus. Years AD are counted forward since that epoch and years BC are counted backward from the epoch. There is no year zero in this scheme; thus the year AD 1 immediately follows the year 1 BC. This dating system was devised in 525 by the Eastern Roman monk Dionysius Exiguus but was not widely used until the 9th century. Modern scholars believe that the actual date of birth of Jesus was about 5 BC.

The 1st century BC, also known as the last century BC and the last century BCE, started on the first day of 100 BC and ended on the last day of 1 BC. The AD/BC notation does not use a year zero; however, astronomical year numbering does use a zero, as well as a minus sign, so "2 BC" is equal to "year –1". 1st century AD (Anno Domini) follows.

In the course of the century, all the remaining independent lands surrounding the Mediterranean Sea were steadily brought under Roman control, being ruled either directly under governors or through puppet kings appointed by Rome. The Roman state itself was plunged into civil war several times, finally resulting in the marginalization of its 500-year-old Roman Republic, and the embodiment of total state power in a single man—the Roman emperor.

The 1st millennium BC, also known as the last millennium BC, was the period of time lasting from the years 1000 BC to 1 BC (10th to 1st centuries BC; in astronomy: JD 1356182.5 – 1721425.5). It encompasses the Iron Age in the Old World and sees the transition from the Ancient Near East to classical antiquity.

World population roughly doubled over the course of the millennium, from about 100 million to about 200–250 million after the birth of Jesus Christ and the establishment of the Julio-Claudian dynasty led by its founder Octavian.