I. Century

1 00th century, the number before the hundred digits is added with1,such as 1069 (Wang Anshi's reform),10+1=1,so it is1. Example: 22 BC1(the establishment of the Qin dynasty), 2+ 1=3, so the 3rd century BC; Example: In 27 BC (when the Roman Empire was founded), 0+ 1= 1, so BC 1 century; Example: In the 9th year of the Western Han Dynasty, 0+ 1= 1, so it was 1 century.

Second, age.

1. Early (early): the first 20 years of this century: the beginning of the 20th century, about1900-1919; Exodus: 594 BC (the first tax mu was implemented in Lu), at the beginning of the 6th century BC. ?

2. The first half: the first half of the century: 1800- 1850 or so,1the first half of the ninth century. ?

3. Mid-term: 40-60 years, for example: 1856 (the second opium war began),1mid-9th century.

4. The second half: 1950s, such as 185 1 year-1899,65438+the second half of the 8th century. Such as: AD 20-29, 65438+1920s; 1980-ad 1989 was the 1980s. 20 ~ 29 years is called the 1920s, 30 ~ 39 years is called the 1930s, …, 90 ~ 99 years is called the 1990s.

Third, the calculation involves the time before and after crossing AD.

It is different from simply calculating the time after BC or AD, that is, one year must be subtracted from the calculated total time. For example, to calculate the number of years between 84 1 and 1949 BC, the correct calculation method is 841+1949-1= 2789. This algorithm can be summarized.

The reason why we want to reduce one year here is that the year of A.D. has not been designated as one year, so we can't calculate the time around A.D. according to the mathematical concept of positive and negative numbers.

Extended data

Staging of China history;

1, Modern History of China: 1840 The First Opium War-1919 May 4th Movement.

1840 The Opium War was the dividing point between ancient history and modern history, which marked the transformation of China from an independent feudal society to a semi-colonial and semi-feudal society.

2. Modern history of China: 19 19-1949.

19 19 the may 4th movement is the dividing point of modern history, which marks the transformation of China revolution from the old democratic revolution to the new democratic revolution.

3. Modern history of China: From 65438 to 0949, the modern history of China including People's Republic of China (PRC) (PRC) was established.

References:

Baidu Encyclopedia-Year

Baidu encyclopedia-century