For other uses, see Century (disambiguation). "Centuries" redirects here. For other uses, see Centuries (disambiguation). "Centenary", "Centennial", and "Centennials" redirect here. For other uses, see Centenary (disambiguation), Centennial (disambiguation), and Centennials (disambiguation). Look up century in Wiktionary, the free dictionary. This article includes a list of references, related reading 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. It is also a Roman term. Centuries are numbered ordinally in English and many other languages (e.g. "the 7th century AD/CE"). Contents 1 Start and end in the Gregorian Calendar 1.1 1st century BC and AD 2 Dating units in other calendar systems 3 Centuries in astronomical year numbering 4 Alternative naming systems 5 Notes and references 6 See also // Start and end in the Gregorian Calendar

According to the Gregorian calendar, the 1st century AD/CE started on January 1, 1 and ended on December 31, 100. The 2nd century started at year 101, the 3rd at 201, etc. The n-th century started/will start on the year (100×n)-99 and ends in 100×n . 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). 1st century BC and AD There is no "zeroth century" in between the 1st century BC and the 1st century AD . Also, there is no 0 AD.1 The Julian calendar "jumps" from 1 BC to 1 AD. The 1st 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 1st century in these calendars may designate the years 0 to 99 as the 1st century, years 100 to 199 as the second etc. However, in order to regard 2000 as the first year of the 21st 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, Danish, Norwegian 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), Danish and Norwegian nittenhundredetallet (or 1900-tallet) 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, meaning the years 1980–1989). Notes and references ^ Two separate systems that also do not use religious titles, the astronomical system and the ISO 8601 standard do use a year zero. The year 1 BC (identical to the year 1 BC) is represented as 0 in the astronomical system, and as 0000 in ISO 8601. Presently, ISO 8601 dating requires usage of the Gregorian calendar for all dates, however; whereas astronomical dating and Common Era dating allow usage of the Julian calendar for dates before 1582 AD.

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