​B.C.- Before Christ- This term designates events that happened prior to the birth of Jesus of Navareth. Ancient times.

A.D.​- Anno Domini (often wrongly assumed to be "After Death")- This Latin term means In the Year of Our Lord. This designation means that the event happened after the birth of Jesus of Navareth.

As should be obvious, these terms are related to Christianity. In the modern world we live in, religious references can sometimes cause issues with those that have differing beliefs or no belief system at all. For this reason, in recent years new terms have been used to designate these periods.

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B.C.E.- Before Common Era- This term is the modern term for anything that happened during​ Ancient times. Replaces B.C.

C.E.- Common Era- This term is the modern term for anything that happened during modern times. Replaces A.D.​

​Important Terms...

Something to keep in mind is how we count the years within each of these periods.

It can be thought of as a number line that you would use in Math, just without the minus sign.

​A.D./C.E. would be on the positive side of the 0 and B.C./B.C.E. would be on the negative side. Just as with a time line, the numbers get higher as you get further from the 0

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300 B.C.<--200 B.C.<--100 B.C.<--0-->100​ A.D.-->200 A.D.-->300 A.D.

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​Decades and Centuries and Millenniums... Oh My!

A Decade is a ten year period. For instance, 2012 to 2022 is a decade.

A Century is a one hundred year period. 1922 to 2022 is a century.

A Millennium is a one thousand year period. 1022 to 2022 is a millennium.

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​The Confusion of Centuries

​You will often hear people refer to the Century that something occurred in as the XXth Century. For example, we are living in the 21st century. But wait...we are living in the year 2022...wouldn't that be the 20th Century? Think about the timeline...

3 B.C.<--2 B.C.<--1 B.C.<--0-->1 A.D.-->2 A.D.-->3 A.D.​

The timeline starts at 0, so the first century actually occurs ​at 0, which leaves 1 A.D as the 2nd Century. This throws our count of Centuries off by one for each century. So, we might live in 2022, but we are living in the 21st Century.

One more thing of note, to distinguish between 1 B.C. and 1 A.D. when talking about Centuries we would say the 1st century B.C. or the 1st century A.D.​

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One more term and a clarification...

​Circa​- This term is used when an exact date cannot be determined. So, if someone says that something happened circa 1986 they are saying that it happened sometime around that year but it cannot be said without a doubt that it was 1986.

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It is necessary to understand that other cultures track time differently than we do. Our system is based in Christian beliefs of the birth of Jesus. There are many cultures that do not believe this. Muslims, Jews, and the Chinese all follow a calendar that differs from our own because their belief system differs from ours.

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