Era refers to the start date of calendar year in history. Most countries in the world adopt the year of A.D., which was originally called the Christian era. The year of Jesus' birth is the beginning of the year, and the year before A.D. is BC.

China era began in the first year of the Western Zhou Dynasty (84 BC1). Since the first year of Emperor Jian Yuan of the Han Dynasty (BC 140), emperors of all dynasties have established the era of year number, that is, the first year or the following year when the emperor ascended the throne or changed the year number halfway is the first year.

Gongyuan times

Also known as cristiana. The era of AD began in the year when the legendary Jesus Christ was born. More than 65,438+0,000 years ago, a Christian monk named Dian verified that 532 AD was the first year of the reign of Emperor Ping of the Western Han Dynasty in China. Therefore, this year should be 532 AD, when China was in the Southern Dynasties and Liang Wudi was in Datong for four years.

At first, this chronology was only used in the church, and it was not gradually adopted by European countries until the16th century. After the first year of AD, the years are numbered sequentially, such as AD 2 and AD 3; Before the first year of A.D., it is called pre-Christ (BC), and the years are counted backwards, such as BC 1 and BC 2.

Between the first year of AD and BC 1 year, there is no year of AD 0. Therefore, the rule that all AD years divided by 4 and 400 are leap years does not apply to BC.

The above contents refer to Baidu Encyclopedia-A.D. Times.