This page is about centuries as units of time. For other meanings of the term, see Century (disambiguation). For a list of centuries, see Centuries.

A century (From the Latin cent, one hundred) is one hundred consecutive years.

• In all dating systems, centuries are essentially numbered ordinally. Thus, the first century of a time frame is "The First Century" and not "Century 0".
• There is considerable disagreement about whether to count the centennial year (e.g. 2000) as the first or last year of a century. This confusion is documented for every centennial year from 1500 onward, and almost certainly arises from the introduction of Hindu-Arabic numerals and the concept of zero to Western Europe in the twelfth century.

The oldest dating systems were regnal, and considered the date as an ordinal, not a cardinal number. Thus, one speaks of the first year of the reign of King John for example. Obviously, the century problem does not arise in such systems. Somewhat later, systems arose dating from the founding of a dynasty, city or religion, and these continued ordinal, rather than cardinal, counting. Thus Ab Urbe Condita counts the Year 1 as the founding of Rome; Anno Domini as the first full year of Jesus Christ's life; the Islamic calendar as the year of the Hijra, so it is also Latinized as Anno Hegirae, or "year of the Hejira."

In the Gregorian calendar, the calendar that is currently used for most purposes nearly everywhere in the world, the first year is that of the traditionally accepted year of Jesus' birth. There is no "year zero". Accordingly, the first century includes the years 1-100 anno Domini, the first millennium (or period of ten centuries) is the years 1-1000 anno Domini, and so on. So according to this measure year 2000 belongs to the second millennium and the first year of the third millennium and 21st century is 2001.

More modern systems of dating (such as that of astronomical year numbering, used by astronomers) begin with a year zero. In these cardinal dating systems, it is perfectly logical to use 0 to 99 as the first century, and to regard 2000 as the first year of the twenty-first century. The year 0 corresponding then to year 1BC.

References

"The Battle of the Centuries", Ruth Freitag, U.S. Government Printing Office. Available from the Superintendent of Documents, PO Box 371954, Pittsburgh, PA 15250- 7954. Cite stock no. 030-001-00153-9.

EXAMPLE: The year 1900 is still 19th century. The year 1901 is 20th century. The year 2000 is 20th century. The year 2001 is 21st century.

See also

• Centuries
• Annum
• Millennium