How Many Years in A Decade?
Each century is made up of 10 decades, a series of 10 years. Photo KnowInsiders

Each century is made up of 10 decades, a series of 10 years. Like centuries, decades can cover any period of 10 years. But when referencing the Gregorian calendar, a decade begins in a year that ends with one and ends with a year that ends in 0. For example, the 1990s officially began in 1991 and ended in 2000. However, it’s more common for people to start and end a year earlier. In this case, the 1990s began in 1990 and ended in 1999.

Where did the word ‘decade’ come from?

The word “decade” originally stems from the Greek word dekas (δεκάς), meaning “a group of ten.”

This word was transmitted through the Romans, who commonly used the prefix dec- to describe collections of 10 items, such as a decathlon, a collection of 10 athletic challenges, or a decagon, a regular 10-sided polygon. Other divisions of time that derive from Latin include the century (100 years) and the millennium (1000 years).

Technically, any group of 10 years is its own decade. The term “decade” is generally used to refer to periods of time based on the tens digit of the calendar year. So the “1980s” refers to the decade of time between 1980–1989.

Since the Gregorian calendar begins on 1 AD (there is no year 0 in the Gregorian calendar), the first decade of the Gregorian calendar refers to the period of time between 1–10 AD, the second decade refers to 11–20 AD, etc. So, even though “the nineties” refers to the years between 1990-1999 AD, the 200th decade refers to the time between 1991–2000 AD.

An event that recurs every decade is called decennial. Similarly, an event that recurs every 100 years is a centennial event and every 1000 years is a millennial event. For example, the U.S. government administers a census decennially; every 10 years. Many high school and college reunions occur every 10 years as well.

**READ MORE: How Many Days Are In A Week and Why Are There Seven Days?

How Long is a Decade and Why?

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Photo The Week

Decade turned into a piece of the English jargon in 1590 formally. It is essentially used to allude to like clockwork in a century. For example, the 1680s or 1930s, which means the time between 1680-1689.

In the Georgian schedule, many years signify various periods. Their schedule has no zero implying that in the event that you are referencing the 1850s, it is the period between 1851-1860.

The contrast between the Georgian schedule and the standard schedule is seen while deciding explicitly a very long time in a century. For example, normally, the eighties allude to the years between 1980-1989. However, in the Georgian schedule, the 190th decade is between 1981-1990.

The use of decade to represent ten years duration has empowered humankind to separate huge chronicled occasions without any problem. Many years have permitted people to rapidly recognize explicit past occasions, for instance, the 40s or 30s, which implies the 1940s and 1930s, separately.

Why is Decade 10 Years Long?

How Many Years in A Decade?

The word decade is from the Greek word ‘dekas,’ which means a gathering often. The word decade was utilized by the Romans, who utilized the syllable dec-to distinguish things assembled in tens: E.G., decathlon, decagon. The two terms depict an assortment of ten things. The word dec-was, thusly, consolidated into the schedule to show the circumstance of 10 years.

Significance of a Decade

Almost all historical incidents are divided in decades; this makes it easier for people distinguish events occurring in a specific time during the past. In addition to the historical events, age can also be classified into decades.

Name of the period

Number of Years it covers

Someone in their





The 20s



The 30s



The 40s



The 50s



The 60s



The 70s



The 80s



The 90s


100 and above

Calculating the decade

There are two ways in which decade can be calculated.

One opinion or formula for calculating the decade is that the start of the decade should be calculated where a year end is 0 for example 1890 is the start of the decade but the decade end should be the year where it ends with the number 9.

As such it is 1980 to 1989. Likewise, 20th centuries’s 2020 of 21st century.


There are various words for the people in each decade of age. These prefixes used in such terms are always from the Latin.

Denarian is the one whose age is between 10 and 19.

Vicenarian: a person whose age ranges from twenty to twenty nine; someone in his or her 20s. Word vicenarian is originated from Latin word “vicenarius” which means “of or containing twenty”.

Tricenarian is someone whose age lies in between thirties, which is thirty to thirty nine years.

Quadragenarian is a person with in the age of 40 to 49, or someone in his/ her forties (40s).

A person who is in his 50s (age 50 to 59) is known as Quinquagenarian.

Sexagenarian: a person whose age is between 60 and 69, inclusive; someone in their 60s.

Septuagenarian is a person whose age is between 70 and 79; someone in his or her 70s. Septuageni is the Latin word which means seventy.

A person in his 80s, which means his or her age rages from 80 to 89, is called as octogenarian.

Nonagenarian is someone in his/ her 90s that is in between 90 to 99.

Centenarian is a person who has reached the age of 100 years. He is called centenarian till the age of 109.

Supercentarian is a person with the age of 110 or older (no upper age limit is defined). This term was coined in 1991. There are only a few people who have lived to age 115.

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