When calculating historical years, we should remember that there is no concept of zero year in historical years, so we should pay attention to the problem of adding and subtracting one when calculating with mathematical principles.

1, the year of the Republic of China and the year of the AD should have been based on the first year of the Republic of China, that is, 19 12, but there is a problem of adding and subtracting one in the calculation. So for the convenience of calculation, we usually use 19 1 1 year as the actual reference. For example, in the twenty-sixth year of the Republic of China, it was191+26 =1937; 1945 is1945-1911= 34 years of the Republic of China.

2. If they are between AD XX and AD XX, or between BC XX and BC XX, it is very simple to directly calculate with mathematical principles. For example, the difference between A.D. 1949 and A.D. 2009 is 2009- 1949=60 years; The difference between 600 BC and 400 BC is 600-400 years =200 years.

If one is in XX BC and the other is in XX AD, then there is a problem of adding and subtracting one. For example, the difference between 2009 BC and 2009 AD is 2009+2009- 1=40 17. (There is no zero year)