Jian 'an was the title of Emperor Xian of Han Dynasty in the late Eastern Han Dynasty. From 196 to 1 until March 220. During this period, the political power of the Eastern Han Dynasty was mainly in the hands of Cao Cao, and many literary leaders in this period were Cao family figures. In literature, Jian 'an literature, represented by Cao Shi and his son, was formed under the impetus of Cao Cao and his son.

Wang Chen's three ancestors were Cao Wu of Wei, Cao Pi of Wei Wendi, Cao Cao of Wei Mingdi, Cao Zhi and Jian 'an of Chen Wangsi, which was the most wonderful period in the history of the late Han Dynasty. During this period, some famous battles took place, such as the battle of Guandu, the battle of Battle of Red Cliffs and Weinan.

The origin of the year number:

The title of the year is used by the feudal dynasty of China to record the year. Usually initiated by the monarch. There was no title from pre-Qin to early Han Dynasty. After Emperor Wu of the Han Dynasty ascended the throne, the title began to be used. In the history of China, it was originally called Jianyuan. Since then, a system has been formed. Emperors of all previous dynasties have to change their titles when they encounter great events, such as good or bad luck, internal troubles and foreign invasion.

The titles of an emperor range from one to a dozen. For example, Tang Gaozong has 14, and most emperors in Ming and Qing dynasties have titles. Therefore, later generations used titles as the titles of emperors, such as Emperor Yongle and Emperor Kangxi. If the first emperor died in the middle of the year, the successor will still use the current title, and the title will be changed after the New Year. For example, in July of the 22nd year of Yongle, Zhu Gaochi ascended the throne in August, and the following year.

The year number system originated in China. Later Silla, Korea, Japan in the late 7th century, and Vietnam in the10th century all began to use year numbers because of the influence of China. In ancient Vietnam, Korea during the Korean Empire and Korea and Mongolia in the early days of the founding of the People's Republic of China were all influenced by China, and they all used the year number, while Japan, which still maintained the imperial system, still used the year number as the order.

However, China, South Korea and Viet Nam completely abolished the title because they abolished the imperial system. In addition, the year of the Republic of China used by the former Republic of China and the main year used by North Korea are often mistaken for the year number.