Tool to find the century for a given year. A century is equal to a period of 100 years, it is important to know the number of the century of a year to replace it in a chronology for example.

Century of a Year - dCode

Tag(s) : Date and Time

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A century is a measure of time corresponding to a period of 100 years.

The calculation of centuries is carried out as follows: Subtract 1, divide the year by 100 then add 1, the integer part is the century.

__Example:__ The year `1987` is 20th century because `1987-1=1986`, `1986/100=19.86`, `19.86+1=20.86`, the integer part is `20`.

Even if 0 century have passed, the first century starts the 1st january of year 1 (there is no year 0 in any Gregorian or Julian calendar).

The second century starts 100 years later, so the first january 101 and so on, the 21st century starts the 1st of january 2001 (as the 3rd millennium), so currently humanity lives in the 21st century.

BC, the principle is reversed, the 1st century BC. JC corresponds to a period beginning on January 1 -100 and ending on December 31 -1, inclusive.

The calculation is therefore slightly different: add 1, divide the year by 100 then add 1, the integer part is the century.

__Example:__ Year -432 is in the 5th century BC (BC) because `-432+1=-431` then `-431/100=-4.31` and `-4.31+1=5.31`, the integer part is `5`.

The difficulty encountered in counting/calculating centuries is due to a common confusion about the measurement of time:

Is a child born today 0 days old or 1 day old? Is it 0 months old or 1 month old? Is it 0 or 1 year old? The correct answer is 0 day, 0 month, 0 year.

On the other hand, the child is currently in the 1st day, of its 1st month, of its 1st year, of its first century.

Between year 1 and year 1000 included, it is the first millennium. Between the year 1001 and the year 2000 is the second millennium. Between the year 2001 and the year 3000 is the third millennium (started on January 1, 2001 and will end on December 31, 3000) so currently humans are in the 3rd millennium.

Here is the formula to work out the century corresponding to a date, extract the year from the date.

__Example:__ The date `14/07/1789` has the year `1789`

Cut out the date at the last 2 digits.

__Example:__ `1789` is broken down into `17` (the first digits) and `89` (the last 2 digits)

If the last 2 digits of the year are between `01` and `99` (inclusive) then the century is the number made up of the first digits plus 1.

Otherwise if the last 2 digits of the year are `00` then the century is the number formed by the first digits.

__Example:__ `89` is between `01` and `99` so the date `14/07/1789` is in the 18th century (18th century in Roman numerals).

Repeat the calculation used for the century but with the last 3 digits and compare them between `001` and `999`.

Take the value in years and divide by 100.

__Example:__ For 250 years, do 250/100 = 2.5 so 250 years is equal to 2.5 centuries

Humanity is currently in the 21th century which began on January 1, 2001 and will end on December 31, 2100.

Add 1 to the first 2 digits (on the left) of the year of birth, unless it is a year that ends in `00`.

__Example:__ `1999` => 19 + 1 = 20 => 20th century

__Example:__ `2000` => 20 => 20th century

__Example:__ `2001` => 20 + 1 = 21 => 21st century

There was no century 0, so on January 1st of year 1 the first century began. 100 years later, on January 1 of the year 101 began the second century and 100 years later, on the 1st of January of the year 201 began the third century. There is therefore a relation between the digit of hundredths in a date and the number of the century. The number of the century is equal to the number of hundreds increased by 1. (Except for the years ending with `00`).

In order to replace the expressions *before Jesus Christ* and *after Jesus Christ*, it is more and more common to use *before our era*, or *before common era (AEC)* for negative years and likewise *common era (EC)* for recent positive years.

There are 100 years (hundred) in a century and 1000 years (thousand) in a millennium. These units are common in history.

Beyond that, it is common to use the unit of a million years or even a billion years, especially in Astronomy or science in general.

There are 10 centuries (of 100 years) in a millennium (of 1000 years).

Use the dCode function to convert centuries to roman numerals.

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Cite as source (bibliography):

*Century of a Year* on dCode.fr [online website], retrieved on 2024-09-09,

- Year to Century Converter
- Century to years converter
- What is a century? (Definition)
- How to count centuries?
- How to find the century of a negative year?
- Why is the calculation of centuries difficult?
- How to count milleniums?
- How to find the century of a date?
- How to find the millenium of a date?
- How to calculate an age in centuries?
- What century is it now?
- How to know a birth century?
- Why add 1 for the century?
- What does CE and BCE mean?
- How many years are there in a century or a millenium?
- How many centuries in a millenium?
- How to write centuries in roman numerals?

century,calendar,age,year,millennium

https://www.dcode.fr/centuries

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