Time in China
The time in China follows a single standard time offset of (eight hours ahead of Coordinated Universal Time), even though China spans almost five geographical time zones. The official national standard time is called Beijing Time (BJT, ) domestically and China Standard Time (CST) internationally. Daylight saving time has not been observed since 1991. China Standard Time (UTC+8) is consistent across China Mainland, Hong Kong, Macau, and Taiwan. History. In the 1870s, the Shanghai Xujiahui Observatory was constructed by a French Catholic missionary. In 1880s officials in Shanghai French Concession started to provide a time announcement service using  the Shanghai Mean Solar Time provided by the aforementioned observatory for ships into and out of Shanghai. By the end of 19th century, the time standard provided by the observatory had been switched to GMT+08:00. The practice has spread to other coastal ports, and in 1902 the "Coastal Time" was proposed to be the universal time zone for all the coastal ports in China. However, the time zone for the rest of China remained undetermined. Until 1913, the official time standard for the whole of China was still the apparent solar time of Beijing, the capital of the country at  the time. Starting in 1914, the Republic of China government began adopting the Beijing Local Mean Solar Time as the official time standard. By 1918, five standard time zones had been proposed by the Central Observatory of Beiyang government of Republic of China, including the Kunlun (), Sinkiang-Tibet (), Kansu-Szechwan (), Chungyuan (), and Changpai (). After the defeat of Beiyang government in 1928, the mission of the Central Observatory was moved to Nanjing, and the reference time standard used for the construction of traditional Chinese Calendar was shifted from Beijing Mean Solar Time to . In the 1930s, the proposed five time zones  had not been fully observed, causing regions in inner China area to adopt their own time standards, resulting in chaos. On 9 March 1939, when the Ministry of the Interior organized a Standard Time Conference in Chongqing, it was decided to adopt the five time zone proposal with slight modification of their borders starting from 1 June, however it was also decided that the entire country would use the Kansu-Szechwan Time () during the Second Sino-Japanese War which began at the time. Following the end of World War II, the five time zone system was resumed, although there is  little information about the historical usage of time in the Kunlun and Changpai zones. A further refined system with adjustment to zone assignment in the Northwest part of Gansu was announced in 1947 for adoption in 1948. However, as the Chinese Civil War came to its end in 1949–1950, regional governments under the influence of the Communist Party of China, other than those in Xinjiang and Tibet, switched to use the same time as Beijing, which is , and is later known as Beijing Time or China Standard Time. There are two independent sources that claim the Communist Party of China , and/or the People's Republic of China, were using apparent solar time for Beijing Time before the period between 27 September 1949 and 6 October 1949, and they adopted the time of within that period of time, but the claim is dubious. Time zone changes in Tibet are undocumented, but Beijing Time was in use until at least the mid-1950s. Between 1969 and 1986, the time zone was switched repeatedly between Xinjiang Time () and Beijing Time. Daylight saving time was observed from 1945 to 1948, and from 1986 to 1991. In 1997 and 1999, Hong Kong and Macau were transferred  to China from the United Kingdom and Portugal respectively, being established as special administrative regions. Although the sovereignty of the SARs belongs to China, they retain their own policies regarding time zones for historical reasons. Due to their geographical locations, both are within the time zone, which is the same as the national standard, Beijing time. Geography. As an illustration of the wide range, the daylight hours (Beijing Time) for the seats of the westernmost (both including and not including Xinjiang due to local customs, see below) and easternmost counties, calculated for the year 2010, are shown here: The border  with Afghanistan at the Wakhjir Pass has the most significant official change of clocks for any international land frontier: in China to in Afghanistan. Regions with special time regulations. Xinjiang. In Xinjiang, two time standards are used in parallel, namely Beijing Time and Xinjiang Time. Xinjiang Time, also known as Ürümqi Time (), is set due to its geographical location in the westernmost part of the country. The time offset is , which is two hours behind Beijing, and is shared with neighbouring Kazakhstan and Kyrgyzstan. Some local Xinjiang authorities now use both time standards side by side. Television stations schedule programmes  in different time standards according to their nature. The coexistence of two time zones within the same region causes some confusion among the local population, especially when inter-racial communication occurs. When a time is mentioned in conversation between Han and Uyghur, it is necessary to either explicitly make clear whether the time is in Xinjiang Time or Beijing Time, or convert the time according to the ethnicity of the other party. The double time standard is particularly observable in Xinjiang Television, which schedules its Chinese channel according to Beijing time and its Uyghur and Kazakh channels according to Xinjiang  time. Regardless, Beijing Time users in Xinjiang usually schedule their daily activities two hours later than those who live in eastern China. As such, stores and offices in Xinjiang are commonly open from 10am to 7pm Beijing Time, which equals 8am to 5pm in Ürümqi Time. This is known as the work/rest time in Xinjiang. In most areas of Xinjiang, the opening time of local authorities is additionally modified by shifting the morning session 30–60 minutes earlier and the afternoon session 30 minutes later to extend the lunch break for 60–90 minutes, so as to  avoid the intense heat during noon time in the area during summer. Hong Kong and Macau. Hong Kong and Macau maintain their own time authorities after transfer of sovereignty in 1997 and 1999 respectively. The Hong Kong Time () and Macau Standard Time (; ) are both all year round, thus in line with Beijing time, and daylight saving time has not been used since 1979 in Hong Kong and 1980 in Macau. In Hong Kong, Greenwich Mean Time was adopted as the basis in 1904, and UTC was adopted as a standard in 1972. Before that, local time was determined by astronomical  observations at Hong Kong Observatory using a . IANA time zone database. The territory of the People's Republic of China is covered in the IANA time zone database by the following zones. "Asia/Shanghai" is used instead of "Asia/Beijing" because Shanghai is the most populous location in the zone. Columns marked with * are from the file zone.tab of the database. Backward compatibility zone. The following zones, including Asia/Kashgar, Asia/Chongqing, and Asia/Harbin, are kept in the "backzone" file of the IANA time zone database for backward compatibility.