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A century (from the Latin centum, meaning one hundred; abbreviated c.[1]) is a period of 100 years. Centuries are numbered ordinally in English and many other languages.

A centenary is a hundredth anniversary, or a celebration of this, typically the remembrance of an event which took place a hundred years earlier.

Start and end in the Gregorian calendar

Although a century can mean any arbitrary period of 100 years, there are two viewpoints on the nature of standard centuries. One is based on strict construction while the other appeals to popular culture.

According to the strict construction of the Gregorian calendar, the 1st century AD began with the year 1 and ended with the year 100. The 2nd century started with the year 101, the 3rd with 201, etc. The n-th century started/will start on the year (100 × n) − 99 and ends in 100 × n.[2] Because of this, a century will only include one year, the centennial year, that starts with the century's number (e.g. 1900 was the last year of the 19th century).

Popular culture aligns centuries with decades, by grouping years based on their shared digits. For example, the 20th century is commonly considered to be from 1900-1999, since all those years begin with 19. This is sometimes known as the odometer effect. The astronomical year numbering and ISO 8601 systems both contain a year zero, therefore centuries would begin in years ending in '00' and conclude with years ending in '99'.

Viewpoint 1: Strict usage

2 BC 1 BC 1 2 3 4 5 ... 96 97 98 99 100 101 102 103 ... 198 199 200 ... 1901 1902 ... 1998 1999 2000 2001 2002 2003 ... 2098 2099 2100 2101 2102 2103 ... 2198 2199 2200
1st century 2nd century ... 20th century 21st century 22nd century

Viewpoint 2: Common usage

2 BC 1 BC 1 2 3 4 5 ... 96 97 98 99 100 101 102 103 ... 198 199 ... 1900 1901 1902 ... 1998 1999 2000 2001 2002 2003 ... 2098 2099 2100 2101 2102 2103 ... 2198 2199
1st century 2nd century ... 20th century 21st century 22nd 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 year 0 AD.[3] The Julian calendar "jumps" from 1 BC to 1 AD. 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, the Aztec calendar, and the Hindu calendar have cycles of years that are used to delineate whole time periods; the Hindu calendar, in particular, summarizes its years into groups of 60,[4] while the Aztec calendar considers groups of 52.[5]

Centuries in astronomical year numbering

The 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.[6]

Alternative naming systems

In Swedish, Danish, Norwegian, Icelandic and Finnish, besides the ordinal naming of centuries another system is often used based on the hundreds part of the year, and consequently centuries start at even multiples of 100. For example, Swedish nittonhundratalet (or 1900-talet), Danish nittenhundredetallet (or 1900-tallet), Norwegian nittenhundretallet (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 referred to as the nineteen hundreds (1900s) four digits begging with a 19. This is similar to the English decade names (1980s, meaning the years 1980–1989) two digits begging with a 8.

See also


  1. ^ "Oxford English Dictionary – List of Abbreviations". 
  2. ^ "The 21st Century and the 3rd Millennium". aa.usno.navy.mil/. U.S. Naval Observatory. 14 June 2011. Retrieved 11 September 2012. 
  3. ^ 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,[citation needed] whereas astronomical dating[citation needed] and Common Era dating allow usage of the Julian calendar for dates before 1582 AD.
  4. ^ "www.vedavidyalaya.com". Retrieved 4 September 2013. 
  5. ^ "www.aztec-history.com". Retrieved 4 September 2013. 
  6. ^ https://eclipse.gsfc.nasa.gov/SEhelp/dates.html


  • 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.
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