Millennium refers to the time span of 1000 years. For example, 1 millennium refers to 1000, 2000 refers to100/to 2000, and 3000 refers to 200 1 to 300. For example, 1 Millennium Index 1 to 1000, 2000 Millennium Index100/to 2000.

When the world celebrated the arrival of the new millennium in 2000, there was a debate about whether 2000 or 200 1 year was the beginning of the new millennium. One school thinks that the solar calendar begins with 1, so 1 to 1000 is the first millennium, and the second millennium begins with 65438.

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The word millennium comes from the Latin Millennium, which means the time span 1000 years, equivalent to 10 century.

In the field of history and social life, the units of measurement greater than years are years, centuries, millennia and millions of years, among which the first three are commonly used. However, in their matching and coordination with the years, the problems have not been completely solved, because they are not based on celestial movements or other movements, but are artificially stipulated and established, so they can be so agreed or established, and solving these problems requires the participation and recognition of the whole society.