The eastern hemisphere in AD 1
Germanic tribes in Europe in AD 1
AD 1 (I), 1 AD or 1 CE is the epoch year for the Anno Domini calendar era. It was the first year of the Common Era (CE), of the 1st millennium and of the 1st century. It was a common year starting on Saturday or Sunday,[note 1] a common year starting on Saturday by the proleptic Julian calendar, and a common year starting on Monday by the proleptic Gregorian calendar. In its time, year 1 was known as the Year of the Consulship of Caesar and Paullus, named after Roman consuls Gaius Caesar and Lucius Aemilius Paullus, and less frequently, as year 754 AUC (ab urbe condita) within the Roman Empire. The denomination "AD 1" for this year has been in consistent use since the mid-medieval period when the anno Domini (AD) calendar era became the prevalent method in Europe for naming years. It was the beginning of the Christian/Common era. The preceding year is 1 BC; there is no year 0 in this numbering scheme. The Anno Domini dating system was devised in AD 525 by Dionysius Exiguus.
The Julian calendar, a 45 BC reform of the Roman calendar, was the calendar used by Rome in AD 1.