Century

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

Centenary redirects here. For the group of suburbs in Brisbane, Australia, see Centenary Suburbs

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

• In all dating systems, centuries are essentially numbered ordinally, and not cardinally. Thus, the first century of a time frame is "The First Century" and not "Century 1," "The Second Century" and not "Century 2," and so on.

• 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 number zero: there is only a "moment/instant zero": the birth of Jesus. Accordingly, the first century includes the years 1-100 anno Domini, the first millennium (or period of ten centuries) comprises years 1-1000 anno Domini, and so on. So, according to this measure, year 2000 belongs to the second millennium. Therefore, the first year of the third millennium (the first year of 21st century) is year 2001: both the third millennium and the 21st century began at the first second of the first minute of the first hour of the first day of year 2001.

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.

More modern systems of dating (such as that of astronomical year numbering, used by astronomers) begin with a year number zero (comprising not only the precise moment of Jesus' birth, but rather the whole year). 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 1 BC. However, even though at first glance this system seems to makes things easier, it actually complicates and confuses matters even further. It is not so clear what to do with the centuries for the negative years in this system. Moreover, if we assume a purely mathematical, "scientific" perspective, it is not even clear that the centuries for the positive years should work the way they are commonly assumed to work as previously described. For example, if we take the first century to comprise years 0 to 99, then the preceding century would comprise years −100 to −1, and the previous one to this would comprise years −200 to −101; that is, the "problem" causing controversy with the traditional year numbering system remains with the negative years of the astronomical year numbering system, and it further introduces the inconsistency that the century-boundary rule works differently depending on whether the years are negative or not. Besides, there is actually no mathematical reason to prefer year 0 (the "zeroth" year?) to be included in the century of years 0 to 99 instead of in the century of years −99 to 0, since number 0 has no sign and thus properly belongs neither in the sequence of positive numbers nor in the sequence of negative numbers, but in a category of its own. Also, should the century before the first century be called "century 0" (the "zeroth" century?) or instead "century −1" (the "minus-first" century, or should it be the "minus-oneth"?). And wouldn't it actually be more "logical" to call the century of years 000 to 099 the "0th century" rather than the "1st century", since the digit at the hundreds position in these years is 0 instead of 1? Or should this reasoning apply to the years −099 to 000, which also have a 0 at the hundreds position? Or, actually, shouldn't this apply to both cases and thus all one hundred and ninety-nine years running from year −099 to year +099 would comprise a "0th double-'century' (of only 199 years)" of sorts, so that the "first century" could be the one of years +100 to +199 and the "minus-first century" the one of years −199 to −100? Or should we make years −099 to −001 the "minus-zeroth 'century' (of only 99 years)", years +001 to +099 the "plus-zeroth 'century' (of only 99 years)", and leave year 000 as a "year without a century" or even as the "unsigned-zeroth century (of only 1 year)?

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.

See also

• List of centuries
• Annum
• Millennium