Task: Question Generation
Input (English): Nanjing ( listen; Chinese: 南京, "Southern Capital") is the city situated in the heartland of lower Yangtze River region in China, which has long been a major centre of culture, education, research, politics, economy, transport networks and tourism. It is the capital city of Jiangsu province of People's Republic of China and the second largest city in East China, with a total population of 8,216,100, and legally the capital of Republic of China which lost the mainland during the civil war. The city whose name means "Southern Capital" has a prominent place in Chinese history and culture, having served as the capitals of various Chinese dynasties, kingdoms and republican governments dating from the 3rd century AD to 1949. Prior to the advent of pinyin romanization, Nanjing's city name was spelled as Nanking or Nankin. Nanjing has a number of other names, and some historical names are now used as names of districts of the city, and among them there is the name Jiangning (江寧), whose former character Jiang (江, River) is the former part of the name Jiangsu and latter character Ning (寧, simplified form 宁, Peace) is the short name of Nanjing. When being the capital of a state, for instance, ROC, Jing (京) is adopted as the abbreviation of Nanjing. Although as a city located in southern part of China becoming Chinese national capital as early as in Jin dynasty, the name Nanjing was designated to the city in Ming dynasty, about a thousand years later. Nanjing is particularly known as Jinling (金陵, literally meaning Gold Mountain) and the old name has been used since the Warring States Period in Zhou Dynasty.
Output (English): When did Nanjing become the Chinese national capital?