How Long is a Decade? Everything you need to know.

Whenever you heard or read any history or past political events, you may have come across the word “Decade”. In this article you will understand “how long is a decade?” and everything about the decade such as the history of decade, exactly how long is the decade? Terminologies other than decades, Important events in the past decades.

Go through this article thoroughly. I am sure, there will not be any confusion regarding decade terminology in your life.

Origin of the word “Decade”?

In ancient Greek “dekas” word was used to identify a group of 10 entities. Later Romans started using the word Decade which was derived from “dekas” via Latin and French.

Exactly how long is a Decade?

A decade is a time span of 10 years. Generally, you can count from any year. There is no specific defined rule, but make sure the time span must be of 10 years. There are different theories and assumptions regarding the start and end year of the decade. Continue reading this article to understand the start and end year of a decade.

How to identify 20, 30, 40, ……. years’ time span?

There are no specific terms to defines 20, 30, 40, … years of time span. But there are some terminologies that are derived from Latin as explained in the below table.

Time Span (Years)In terms of DecadeLatin Name of Time Span
101 DecadeDecennial
202 DecadesVicennial
303 DecadesTrigentennial
404 DecadesQuadragennial
505 DecadesSemicentennial
606 DecadesSexagennial
707 DecadesSeptuagennial
808 DecadesOctogintennial
909 DecadesNonagintennial
10010 DecadesCentennial 

What is century and Millennium?


Century is a period of 100 years or you can say, period of a 10 decades. Currently we are living in a 20th century. In Latin it is called as a Centennial.

1 Century = 10 Decades = 100 Years


Millennium is a period of 10 Centuries or 1000 years or you can say, period of a 100 decades. In Latin it is called as  a Millennial.

1 Millennium = 10 Centuries = 100 Decades = 1000 Years

Why decade is an important terminology to explain history?

As explained above, a decade is a time span of 10 years. Major events that happened in the past can be easily tracked and remember using a decade instead of the exact year. Some events such as world war 1, world war 2, the cold war, and disturbance in Syria happened over a period of certain years. Their causes and impacts can last for over a period of time. It becomes difficult to track or record the exact dates or years of those events. That is why decade terminology becomes so much important while explaining the major events in history.

When does the decade start? 2020 or 2021?

It’s a really interesting topic, probably you might have wondered this couple of times. Whenever we say decade, first thing comes to our mind is the period of 10 years. But have you ever thought when the decade actually starts? This question is important because logically and calendar wise people have different opinions about it.

Let’s try to understand by taking an example of 90’s decade.

When you say 90’s decade, then which time span comes to your mind? 1990 to 1999 or 1991 to 2000?  Years from 1990 to 1991, contains all the years of 90’s series and years from 1991 to 2000, contains 2000 which does not belong to the 90’s series. So logically years from 1990 to 1999 is a correct timespan. By this logic 0-9 is a decade’s time span.

But when you see a calendar, there is no 0th year. Years started from 1 to the current year, so 1 to 10 is the correct time span to decide a decade. This way, the years from 1991 to 2000 are called the 90’s decade. So, up to you how you want to take it.

Important events from 19th century decades to the current decade in world history:

Decade PeriodImportant Events
1901 – 1910Airplane invention by wright brothers, Tunguska event
1911 – 1920World War – 1, Russian revolution
1921 – 1930Women’s Suffrage in USA, first time women get to vote, Rise of Chinese communism, Kanto earthquake in Japan, Beginning of a Mickey Mouse era. Stock market crash which lead to depression in USA.
1931 – 1940Rise of Nazis in Germany, Hitler comes to power, persecution of Jews, start of World War – 2 in Poland.
1941 – 1950World War – 2, Cold war between west and Soviet Union, Independence of India, Assassination of Mahatma Gandhi, Rise of Israel.
1951 – 1960Discovery of Polio vaccine, Beginning of civil rights movement in USA.
1961 – 1970Assassination of Martin Luther King, Vietnam War, Soviet Union’s successful space mission.
1971 – 1980Vietnam War, Jonestown Massacre, Munich Olympics massacre, Watergate scandal in USA.
1981 – 1990PATCO Strike, Fall of Berlin Wall, End of cold war, Poison gas leak in Bhopal, Stat of video games and 24 hour news channels, evolution of internet.
1991 – 2000Bombing in Oklahoma City, massacre in Rwanda, Nelson Mandela was released from prison.
2001 – 2010Death of Steve jobs, Revolution in mobile telecommunication, Financial crisis, Crash of share market.
2011 – 2020India won the cricket world cup, United Kingdom’s withdrawal from European Union, Black lives matter movement in USA, Outbreak of Corona Virus


I hope in this article you got to know everything about a decade especially how long is a decade, when the decade actually starts, the history of decade and important events from 19th century decades. I hope by reading this article you got a clear understanding of all aspects of Decade terminology. Do share your thoughts in the comment section refgarding decade to let others know what you think.

Some interesting FAQs about the decade:

How long is a decade and how long is a century?

Decade is a period of 10 years and century is a period of 100 years. That means century is a period of 10 decades.
1 Century = 10 Decades = 100 Years

How long is a decade in days?

Since decade is a period of 10 years, if we convert decade to days, it becomes 3650 days i.e. 365 (1 year) x 10.

How long is a decade and a half?

A decade and a half is a period of 15 years. A decade consists of 10 years and a half decade is 5 years.

How long is a decade on Venus?

In Venus 1 day is equivalent to 243 earth days and 1 year is equivalent to 225 earth days. Venus rotates around itself so slow that it complete onw orbit around the sun before that. So, if we put simple logic, on Venus, a decade would be 225 x 10 = 2250 days.

How long is a decade, century, millennium?

A decade is a period of 10 years. A century is a period of 100 years and a millennium is a period of 1000 years.
1 Millennium = 10 Centuries = 100 Decades = 1000 Years

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