system of dating that was adopted by the Chinese in 140 BCE (retroactive to 841 BCE). The nianhao system was introduced by the emperor Wudi (reigned 141–87 BCE) of the Xi (Western) Han (Han dynasty), and every emperor thereafter gave his reign a nianhao at the beginning of his accession (sometimes a new nianhao was assigned on the basis of signs of a particularly auspicious or ominous nature or on special occasions). The nianhao system persisted until and informally for some years after the establishment of the republic in 1911—the next year of which was considered year one of a new period, with the Republic of China being used as the era name in the nianhao manner. In 1949, upon the founding of the People's Republic of China, the Gregorian calendar was adopted.