BC-before that time all the dates are counted backward are called BC or before Christ(before the birth of Jessus Christ)
AD-the time after birth of Jessus is called AD or anno Domini.

AD and BC in History

The terms AD and BC are commonly used to indicate the timeline of events in history. AD stands for Anno Domini, which means "in the year of our Lord" in Latin, while BC stands for Before Christ. These terms are used to divide history into two main periods: before the birth of Jesus Christ (BC) and after his birth (AD).

AD

AD is used to indicate years after the birth of Jesus Christ. It is based on the Christian calendar, which was developed in the 6th century by a monk named Dionysius Exiguus. According to this calendar, the year of Jesus' birth is considered to be 1 AD, although it is now believed that he was actually born several years earlier.

BC

BC is used to indicate years before the birth of Jesus Christ. It is also based on the Christian calendar, with the year 1 BC being the year immediately before 1 AD. The use of BC dates back to the 16th century, when it was first introduced by a French scholar named Joseph Scaliger.

Differences between AD and BC

There are several key differences between AD and BC:

1. The starting point: AD is based on the birth of Jesus Christ, while BC is based on the period before his birth.

2. The numbering system: AD uses a positive numbering system, with higher numbers indicating more recent years, while BC uses a negative numbering system, with lower numbers indicating more distant years.

3. The year 0: AD does not have a year 0, while BC does. This means that the year immediately before 1 AD is 1 BC, not 0 AD.

4. The use of alternative dating systems: While AD and BC are the most commonly used dating systems, there are alternative systems in use as well, such as the Islamic calendar (AH) and the Chinese calendar (which uses a combination of cycles of years, months, and days).

In conclusion, AD and BC are dating systems used to indicate the timeline of events in history. While they are both based on the Christian calendar, they differ in several key ways, such as their starting point, numbering system, and the presence or absence of a year 0.