Xi'an (Chinese: 西安; pinyin: Xī'ān About this sound listen (help·info)), is the capital of Shaanxi Province, People's Republic of China. It is a sub-provincial city located in the center of the Guanzhong Plain in Northwestern China. One of the oldest cities in China, Xi'an is the oldest of the Four Great Ancient Capitals, having held the position under several of the most important dynasties in Chinese history, including Western Zhou, Qin, Western Han, Sui, and Tang. Xi'an is the starting point of the Silk Road and home to the Terracotta Army of Emperor Qin Shi Huang.
Since the 1990s, as part of the economic revival of inland China especially for the central and northwest regions, the city of Xi'an has re-emerged as an important cultural, industrial and educational centre of the central-northwest region, with facilities for research and development, national security and China's space exploration program. Xi'an currently holds sub-provincial status, administering 9 districts and 4 counties. As of 2015 Xi'an has a population of 8,705,600 and the Xi'an-Xianyang metropolitan area has a population of 13,569,700. It is the most populous city in Northwest China, as well as one of the three most populous cities in Western China. According to a July 2012 report by the Economist Intelligence Unit, it was recently named as one of the 13 emerging megacities, or megalopolises, in China. The report pinpoints and highlights the demographic and income trends that are shaping these cities' development.
Xi'an has rich and culturally significant history. The Lantian Man was discovered in 1963 in Lantian County, 50 km (31 mi) southeast of Xi'an, and dates back to at least 500,000 years before the present time. A 6,500-year-old Banpo Neolithic village was discovered in 1953 on the eastern outskirts of the city proper, which contains the remains of several well organized Neolithic settlements carbon dated to 5600–6700 years ago. The site is now home to the Xi'an Banpo Museum, built in 1957 to preserve the archaeological collection.
Xi'an became a cultural and political centre of China in the 11th century BC with the founding of the Zhou dynasty. The capital of Zhou was established in the twin settlements of Fengjing (丰京) and Haojing, together known as Fenghao, located southwest of contemporary Xi'an. The settlement was also known as Zhōngzhōu to indicate its role as the capital of the vassal states. In 770 BC, the capital was moved to Luoyang due to political unrest.
Xi'an lies on the Guanzhong Plain in the south-central part of Shaanxi province, on a flood plain created by the eight surrounding rivers and streams. The city has an average elevation of 400 metres (1,312 ft) above sea level and an annual precipitation of 553 mm (21.8 in). The urban area of Xi'an is located at 34°16′N 108°56′E. The Wei River provides potable water to the city.
The city borders the northern foot of the Qin Mountains (Qinling) to the south, and the banks of the Wei River to the north. Hua Shan, one of the five sacred Taoist mountains, is located 100 km (62 mi) away to the east of the city. Not far to the north is the Loess Plateau.
At the beginning of Han dynasty, Prime Minister Zhang Liang advised the emperor Liu Bang to choose Guanzhong as the capital of the Han dynasty: 'Guanzhong Plain, which is located behind Xiao Pass and Hangu Pass, connects Long (Gansu) and Shu (Sichuan). Land of thousands miles and rich in harvest can be found here, as if this place is belongs to the nation of the heaven.' (《关中左崤函，右陇蜀，沃野千里，此所谓金城千里，天府之国也》) Since then, Guanzhong is also known as the 'Nation of the Heaven'.
National Time Service Centre
The Shaanxi Astronomical Observatory was established in 1966. In 1975, according to the Geodetic Origin Report of the People's Republic of China, 'in order to avoid bias in the mensuration as much as possible, the Geodetic Origin would be in central mainland China.' Lintong (临潼), a town near Xi'an was chosen. Since 1986, Chinese Standard Time (CST) was set from NTSC. The NTSC in Lintong is 36 km (22 mi) away from Xi'an.
National Time Service Centre (NTSC), the Chinese Academy of Sciences is an institute which is mainly engaged in the service and research on time and frequency. NTSC takes charge of generating and maintaining the national standard time scale, disseminating the time and frequency signals. The autonomous standard time scales of universal time and atomic time and the dissemination techniques with LF radio and HF radio were established successively during the 1970s and 1980s, which meet all the requirements for different applications on the whole, such as the scientific researches, national economy, etc.
Xi'an has a temperate climate that is influenced by the East Asian monsoon, classified under the Köppen climate classification as situated on the borderline between a semi-arid climate (BSk) and humid subtropical climate (Cwa). The Wei River valley is characterised by hot, humid summers, cold, dry winters, and dry springs and autumns. Most of the annual precipitation is delivered from July to late October. Snow occasionally falls in winter but rarely settles for long. Dust storms often occur during March and April as the city rapidly warms up. Summer months also experience frequent but short thunderstorms. The monthly 24-hour average temperature ranges from around the freezing mark in January to 27.0 °C (80.6 °F) in July, with an annual mean of 14.08 °C (57.3 °F). With monthly percent possible sunshine ranging from 31 percent in December to 47 percent in August, the city receives 1,536 hours of bright sunshine annually. Extremes since 1951 have ranged from −20.6 °C (−5 °F) on January 11, 1955 to 41.8 °C (107 °F) on June 21, 1998. A highest record of 42.9 °C (109 °F) was registered in another station on June 17, 2006.