470-544 CE) which provided the groundwork for the later dating system of BC/AD.
("in the year of our Lord") in an attempt to stabilize the date of the celebration of Easter.
There is no year zero in this scheme, so the year AD 1 immediately follows the year 1 BC.
This dating system was devised in 525, but was not widely used until after 800.
This method of dating was continued by the Romans who counted their years according to three different systems in different eras: from the founding of Rome, by which consuls were in power, and by which emperors ruled at a given time.