The ancient history of China started from the Xia Dynasty in 2070 BC to the Opium War in 1840 (the beginning of China's modern history), with a total of 2070+ 1840=39 10 years.
Xia dynasty: about 2029 BC-about 1559 BC, * * * year: 47 1.
Shang dynasty: about 1559 BC-about 1046 BC, * *.
Zhou dynasty: about 65438 BC+0046 BC-256 BC, divided into the Western Zhou Dynasty and the Eastern Zhou Dynasty, and the Eastern Zhou Dynasty was divided into the Spring and Autumn Period and the Warring States Period, and * * * counted as 867 years.
Qin dynasty: 2265438 BC+0-206 BC. Before 22 1 B.C., Ying Zheng, king of Qin, unified the six countries, and was named emperor at the beginning. * * * Year: 16.
Pre-BC algorithm:
The specific algorithm is the first year after BC 1 year, that is, AD 1 year, and there is no year 0, so the algorithm is X+Y- 1 to calculate the time period from X BC to Y AD.
AD is a rule arranged in chronological order. The so-called 20 14 year is the 20th14 year from the first year of AD, and 2020 BC is the 2020th year before the first year of AD.
BC is counted backwards. For example, the Western Han Dynasty was founded in 202 BC, the Qin Dynasty was founded in 22 BC1year, and 202 BC was later than 22 BC1year. It should be noted that the month of BC is still counting, with 1 in front and 12 behind. The date is the same, the first day comes before and the fifteenth day comes after.