century

Look up century in Wiktionary, the free dictionary.

This article includes a list of references or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations where appropriate. (April 2009)

A century (from the Latin centum, meaning one hundred) is one hundred consecutive years. Centuries are numbered ordinally in English and many other languages (e.g. "the seventh century AD").

Start and end in the Gregorian Calendar

According to the Gregorian calendar, the 1st century AD started on January 1, 1 and ended on December 31, 100. The 2nd century started at year 101, the third at 201, etc. The n-th century started/will start on the year 100×n - 99. A century will only include one year, the centennial year, that starts with the century's number (e.g. 1900 is the final year in the 19th century).

End of the 20th century

It is commonly-held misconception that the 20th century ended on December 31, 1999. The 20th century actually ended on December 31, 2000, its centennial year.^{[citation needed]}

1st century AD and BC

There is no "zeroth century" in between the first century BC and the first century AD. Also, there is no 0 A.D. The Gregorian calendar "jumps" from 1B.C. to 1 A.D. The first century BC includes the years 100 BC to 1 BC. Other centuries BC follow the same pattern.

Dating units in other calendar systems

Besides the Gregorian calendar, the Julian calendar and the Hindu calendar have cycles of years which are used to delineate whole time periods; the Hindu calendar, in particular, summarizes its years into groups of 60.

Centuries in Astronomical Year Numbering

Astronomical year numbering, used by astronomers, includes a year zero (0). Consequently, the first century in these calendars may designate the years 0 to 99 as the first century, years 100 to 199 as the second etc. However, in order to regard 2000 as the first year of the twenty-first century according to the astronomical year numbering, the astronomical year 0 has to correspond to the Gregorian year 1 BC.

Alternative naming systems

In Swedish and Finnish centuries are typically not named ordinally, but according to the hundreds part of the year, and consequently centuries start at even multiples of 100. For example, Swedish nittonhundratalet (or 1900-talet) and Finnish tuhatyhdeksänsataaluku (or 1900-luku) refer unambiguously to the years 1900–1999. The same system is used informally in English. For example, the years 1900-1999 are sometimes referred to as the nineteen hundreds(1900s). This is similar to the English decade names (1980s = the years 1980–1989).

References

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

See also

• List of centuries
• Millennium
• Lustrum
• Decade

v • d • e Time measurement and standards Major subjects Time · Chronometry · Orders of magnitude · Metrology Time Portal International standards UTC · UT · TAI · ISO 31-1 · DUT1 · Leap second · IERS · Terrestrial Time · Geocentric Coordinate Time · Barycentric Coordinate Time · Civil time · 12-hour clock · 24-hour clock · ISO 8601 · International Date Line · Solar time · Time zone · Daylight saving time · Time offset Obsolete standards Ephemeris time · Barycentric Dynamical Time · Greenwich Mean Time · Prime Meridian Time in physics Spacetime · Chronon · Cosmological decade · Planck epoch · Planck time · T-symmetry · Theory of relativity · Time dilation · Gravitational time dilation · Coordinate time · Proper time · Time domain · Continuous time · Discrete time · Absolute time and space Horology Clock · Astrarium · Atomic clock · Hourglass · Marine chronometer · Radio clock · Sundial · Watch · Water clock · History of timekeeping devices · Equation of time · Complication Calendar Astronomical · Julian · Gregorian · Islamic · Lunisolar · Solar · Lunar · Epact · Intercalation · Leap year · Tropical year · Equinox · Solstice · Seven-day week · Week-day names · Calculating the day of the week · Dominical letter Archaeology & geology International Commission on Stratigraphy · Geologic Time · Archaeological dating Astronomical chronology Nuclear time scale · Precession · Sidereal time · Galactic year Units of time Second · Minute · Hour · Day · Week · Fortnight · Month · Year · Decade · Century · Millennium · Jiffy · Lustrum · Saeculum · Shake · Tide Related topics Chronology · Duration · System time · Metric time · Mental chronometry · Time value of money · Timekeeper