Why did the Xia Dynasty start to calculate the history of China from 265438 BC+046 BC?

It is pushed back by the current international calendar year. There was no continuous digital chronology in ancient China, but there were four kinds of chronologies in ancient China:

The chronology of the year when a prince ascended the throne is based on the number of years when the prince reigned. Like Zuo Zhuan? The Battle of Cuisine: "In the spring of thirty-three years, the Qin Dynasty crossed the North Gate of Zhou Dynasty." I stayed in Lu Xigong for thirty-three years. Biography of Lian Po and Lin Xiangru: "In the sixteenth year of Huiwen, Lian Po was General Zhao."

The chronological method of year number has a year number since Emperor Wu of Han Dynasty. Since then, every emperor has to change the throne and mark the year with the year number. For example, The Story of Yueyang Tower, Four Years of Qingchun, Pipa, Ten Years of Yuanhe, You Bao Chan Shan, July of the First Year of Yuanhe, Shi Zhongshan, Seven Years of Yuanfeng, Meihualing, Two Years of Shunzhi, Two Years of Deyou, and South Guide.

The chronology of the cadres and branches is like the inscription on the tomb of five people: "Duke Zhou was arrested in Jude and looked forward to Ding Mao's March." "Ding Mao" refers to AD1627; The preface to the story of the seventy-two martyrs in Huanghuagang: "The worst death was the siege of Guangdong and Guangxi on March 29th,191." Xinhai refers to the year1911; "Letter to Wife" "Xin Wei reads six nights and four drums in March" and "Xin Wei" should be Xinhai. In modern times, chronicles of cadres and branches are often used to represent major historical events, such as the Sino-Japanese Sino-Japanese War of 1894-1895, the Reform Movement of 1898, the boxer indemnity, the Sino-Japanese Treaty and the Revolution of 1911.

The title of emperor in the year of law and discipline is placed before the title of emperor, and the title of emperor is placed after the title of emperor. For example, in Yangzhou Slow, "Xichun Shen Bing", "Xichun" is the year number of Zhao Shien in Song Xiaozong, and "Shen Bing" is the main branch year number; In the story of Nuclear Ship, "Apocalypse is the autumn day in Ren Xu", "Apocalypse" is the year number of Zhu Youxiao, and "Ren Xu" is the dry year. Among Salute to Sisters, Ding Haidong, the Crazy Dragon, and Gan Long were written by the Qing Emperor Aisin Jiyoro. Li Hong's year number, "Dinghai" is the year of the main branch; Mei Hua Ling Ji is April of the second year of Shunzhi, and Shunzhi is the ancestor of Qing Dynasty, Aisingiorro? The year number of Fu Lin, "Yiyou" is the year of the main branch.

A. D. is the abbreviation of "Gregorian calendar era", which is an international calendar system.

The legendary birth year of Jesus Christ is the first year of Gregorian calendar (equivalent to the first year of Emperor Ping of the Western Han Dynasty in China). The rise of Christianity in Europe has gradually become the dominant religion. In order to expand the ruling power of the church, a Christian monk named Jonesi strongly advocated the birth of Jesus as the era, which was strongly supported by the church. The year when the Bishop of Rome officially announced the birth of Jesus, the God worshipped by Christianity, was designated as the AD year, so some people called it the Christian era. Before the birth of Jesus, it was called "BC" (the abbreviation of Latin Anno Domini in A.D., meaning "the year of the Lord's birth"), and after the birth of Jesus, it was called "After A.D." (the English abbreviation of BC, meaning "before Christ").

In western countries, the AD calendar year is widely used around 1400. China adopted the Gregorian calendar month and day (19 12) one year after the Revolution of 1911, but at the same time adopted the year of the Republic of China.

The calendar year of People's Republic of China (PRC) adopts the calendar year system of most countries in the world, which was decided at the first plenary session of China People's Political Consultative Conference in September 1949. At the meeting, everyone agreed to adopt the common calendar system in most countries in the modern world, that is, adopt AD as the calendar year of new China. On September 27th, the second of the four resolutions adopted at the first plenary session of the China People's Political Consultative Conference was: "The year number of People's Republic of China (PRC) adopts AD".

There are many dating methods in the world, but at present the most commonly used method in the world is the AD dating method. In addition, there are chronologies of cadres and branches, astronomical chronologies, historical chronologies, and chronologies of emperors' titles. In addition, there are Islamic times, Buddhist times, Jewish times, Greek times, Japanese times and so on.

In China, as early as 2000 BC, it had its own calendar. For a long period of history, China adopted the "era method of cadres and branches", that is, the ten-day cadres and the twelve-day branches were combined into one, and every 60 years was a cycle.

Because the starting point of the AD calendar is 1, there is no "AD 0", so most scientists who have a full understanding of the AD calendar and the most authoritative astronomical institutions in the world clearly support the statement that 2 1 century began at 200 1.