The terms anno Domini (AD) and before Christ (BC) are used to label or number years in the Julian and Gregorian calendars.

How did people know what year it was before BC?

Systems of dating before B.C./A.D. was fully adopted were often based on significant events, political leaders and a well-kept chronology of the order in which they ruled. For example, the Romans generally described years based on who was consul, or by counting from the founding of the city of Rome.

When did years start being counted?

It was on one such table that, in A.D. 525, a monk named Dionysius Exiguus of Scythia Minor introduced the A.D. system, counting the years since the birth of Christ.

What is the year before 1 BC called?

AD 1 The traditionally accepted year of Christs birth is labeled AD 1 and the year before is 1 BC. This calendaring system was devised in AD 525, but was not widely used until after AD 800. An alternative for AD is CE, which stands for Common Era, Christian Era or Current Era.