The Greeks were among the first to try to get everyone running on the same year. D., to coincide with the rise of Roman emperor Diocletian into power. C.—that is, “before Christ”—wasn't introduced until 1627, by a French astronomer. D., so decided to figure that in by counting backwards. The specifics of which one are not particularly important.
They looked into their archives, decided Year One should be an event of cultural importance, and settled on the first year that the Olympic Games were held. C., but for the Greeks—and other countries and cultures under their dominance—that was Year One. They looked into their archives, also decided Year One should be an important event, and decided it should be the founding of the city of Rome, an event that supposedly took place in what we now consider 753 B. The Sumerian calendar re-started Year Ones with the rise of each new king. The last big holdouts were Portugal, which adopted the system in 1422, and the Russian empire, which gave in by 1700. “It could've gone in any number of different ways,” Noreña says.
The Anno Domini year–numbering system was introduced by a Christian monk named Dionysius Exiguus in the 6th century.
The year count starts with year 1 in the Gregorian calendar.
“In the Middle Ages and Antiquity, there were multiple eras jostling for recognition.”The key wasn't what Year One was, as much as getting everyone on the same page. “But because they were so powerful and influential, people picked up their calendar and dating system because it was convenient.”While these were the dominant systems, there was a hodge-podge of various cultures with different Year Ones. “One, they use the same year, so it's the same system.
(Let's not even discuss Year Zero, seeing as this jockeying for Year One position occurred before the concept of zero had even been invented.) If we wanted to allow for commerce, trade, and simple communication across cultures to develop, we needed to be living in the same year. The Byzantine Empire started its first year in what was considered the year of creation (our 5509 B. The Church of Alexandria began its Year One in what is now 284 A. And two, when most people see it, they think it stands for Christian Era and Before Christian Era, so it doesn't really solve the problem people wanted to solve.” As the world continued to “shrink” due to the establishment of trade routes and expansion of population and as once-insular communities started opening up and exploring, a single Year One would have inevitably dominated.
Adding CE or BCE after a year is only necessary if there is room for misunderstanding, e.g.