Century

"Centuries" and "Centenary" redirect here. For other uses, see Century (disambiguation), Centuries (disambiguation), and Centenary (disambiguation).

A century (from the Latin centum, meaning one hundred; abbreviated c.) 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. 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. In this model, the 20th century runs from 1900 to 1999, inclusive. 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'.

In the late 1990s, there was a dispute to whether the 21st century would begin on January 1, 2000, or January 1, 2001. Most people considered the 1999-2000 celebrations to mark the start of the 21st century, with fewer people marking the 2000-2001 celebrations as the starting point.

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: General 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. 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, while the Aztec calendar considers groups of 52.

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.

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).

See also

• Age of Discovery
• Ancient history
• Before Christ
• Common Era
• Decade
• List of centuries
• Lustrum
• Middle Ages
• Millennium
• Modern era
• Saeculum
• Year

Bibliography

• 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.