The concept of time span in developed countries in Europe and America is from1969 (1969 ad) to the future. China and some developing countries refer to the information age from1984 (1984ad) to the future, which is 15 years later than Europe and America. People often use the most representative production tools to represent a historical period and the development of human civilization, such as the Stone Age, Bronze Age, Iron Age, Dark Age, Enlightenment Age, age of steam, Electrical Age and Atomic Age. Looking at the 20th century with this mode of thinking, you will say that in the past 100 years, mankind has moved from the electrical age to the information age.