Usually the past is recorded in centuries. However, the past is also divided into larger periods of time known as eras, ages or periods. Eras and ages are usually made up of more than one century (one hundred years).
When we find out about an age or era, we can learn about what happened at particular time blocks in history, for example the age of the Roman Empire. We can also learn about what was happening in Ireland and around the world during large blocks of time, such as the Old Stone Age, the New Stone Age, the Middle Ages or the Viking Age. We can also learn about life during a similar block of time known as an era, for example the Norman era.
AD and BC
We now live in the 21st century. Christian people invented a way of counting modern time which used A.D. as they started counting time from the time Our Lord was born. In Latin, the most common language long ago, the year Our Lord was born was called “Anno Domini” or AD. This means that the year 300 AD was three hundred years after the birth of Our Lord. For example 2010 A.D. is over two thousand years since it is calculated that Our Lord was born.
Remember: A.D. stands for Anno Domini, which is Latin for "year of our Lord," and it means the number of years since the birth of Jesus.
So what does B.C. mean? Can you guess?
It stands for Before Christ. This counts the number of years before the birth of Jesus. So 450 B.C. means 450 years before Christ or 2450 years ago from today. More than 2,500 years ago was the time of the Ancient Greeks for instance. We can still see evidence of life in ancient Greece today because of the many buildings that still survive, for example the Acropolis, which was built in the 5th century B.C.