China: 'Night-Shining White'. Zhao Ye Bai, a favourite horse of Emperor Xuanzong (712-56). Handscroll painting by Han Gan (706-783), c. 750 CE. Emperor Xuanzong of Tang (8 September 685-3 May 762), also commonly known as Emperor Ming of Tang (Tang Minghuang), personal name Li Longji, known as Wu Longji, was the seventh emperor of the Tang dynasty in China, reigning from 712 to 756. His reign of 43 years was the longest during the Tang Dynasty. In the early half of his reign he was a diligent and astute ruler, ably assisted by capable chancellors like Yao Chong and Song Jing.