What does BC and AD mean in time?

Answer 1

AD stands for "Anno Domini," Latin for "year of the Lord." The year in AD is supposedly counted from the birth of Jesus. However, it was a couple of centuries after the time of Jesus that anyone started numbering the years that way, and thee is no guarantee that the actual year was figured out correctly. BC stands for the English phrase "Before Christ." Some countries use initials of the corresponding phrase in their own language; for example France uses AJC for "avant Jesus-Christ."

Answer 2

BC means Before Christ.
AD means Anno Domini, which is Latin for "in the year of our lord".
Anything that occurred in history before 0 AD was called BC.
For example, the Great Pyramid was built in 2584 BC. And World War Two ended in 1945 AD.


However most people now use the terms BCE and CE instead.
BCE stands for "Before the Common Era".
CE stands for "Common Era".

This is because:

• Not everyone is Christian
• BC and AD is seen as forcing people to believe in the existence of Jesus
  
• If Jesus existed, he was not born in 0 AD anyway (the apparent year was misinterpreted)
• AD doesn't make sense in modern grammar. "12th century in the year of our Lord"

For example, the Great Pyramid was built in 2584 BCE. And World War Two ended in 1945 CE.

Most people, including historians, prefer using BCE / CE over BC / AD.
For professionalism I would advise using BCE / CE.