BC/AD and BCE/CE

The exact history is very vague, because it took hundreds of years for the concept to catch on.

Before it was determined, ancient cultures kept track of their years based on astrology, any important events, and/or how many years a leader had been ruling.

Eventually, a Christian came up with the timeline we use today, and it was adopted by the world over hundreds of years as a common way to keep track of and compare time.

Jesus was obviously incredibly important in Christian Europe.

in 525 A.D., a monk wanted to work out when exactly Easter would occur in the coming years. He formulated a new table of when the holiday would fall, starting from a year he called “532.”

He then used what he thought was the year of Jesus's birth, an important event for Christians, as year 1.

BC = Before Christ

AD = Anno domini - "the year of our lord"