Jianming, Kaiming, Zhongxing, Yongxing, Longtai, Zhengde, etc.
The reign name is a name used by the Chinese feudal dynasty to commemorate the year. Usually initiated by the emperor. There was no era name from the pre-Qin Dynasty to the early Han Dynasty. Emperor Wu of the Han Dynasty created the first era name after he came to the throne. The founding year was Jianyuan. After that, a system was formed. Emperors in the past dynasties generally had to change their reign names when they encountered major events such as "auspicious fortune from heaven" or internal strife and external troubles. An emperor may have as few as one reign title or as many as a dozen.
The era name was initiated in ancient China. When a new monarch came to the throne, in order to distinguish the previous monarch, the new monarch recalculated the number of years in power. When Emperor Wu of the Western Han Dynasty came to the throne, a commemorative name was added before the year, which was the beginning of ancient Chinese era names. According to the "Twenty-Two Historical Notes" written by Zhao Yi of the Qing Dynasty, the era name chronology was first created in the 19th year of Emperor Wu of the Han Dynasty, and the era name was "Jianyuan" (140 BC - 135 BC).
The questioner is probably going to write a time-travel novel. I have the following suggestions for choosing a country name:
1. In ancient times, people were very particular about choosing a country name. Generally, it was the name that the founding monarch first occupied. Name the territory or title. For example, when Liu Bang was granted the title of Hanzhong, he took the title of Han, and when Li Yuan was granted the title of Duke of Tang, he took the title of Tang. Therefore, the area where the territory written by the subject of the question was originally located can be named after the country.
2. Starting from the Yuan Dynasty, the country name can also choose auspicious and atmospheric words in ancient books. This was the case in the Yuan, Ming and Qing Dynasties. The words I recommend include: Rui, Qian, Zhuang, Xuan and other auspicious words. Country name.