# How many years is a decade, a century, a millennium?

The milestones of 1 decade, 1 century, 1 millennium are very familiar to everyone because they appear in daily life, appear everywhere. It's easy to come across when you hear phrases like the 19th century, the 1980s, or spend a millennium. So how many years do these milestones represent? Follow the article to figure it out.

## Millennium, century, decade includes how many years?

By convention of the Gregorian calendar, also known as the Gregorian Calendar, the timelines are formulated into years:

- 1 millennium = 10 centuries = 1000 years
- 1 century = 10 decades = 100 years.
- 1 decade = 10 years = 3652 days.

There are 3 different **ways to calculate millennium** .

Method 1: 1 millennium is calculated from year x001 - y002 ie millennium I from year 1 to 1010, the second millennium from 1002 to 2002.

Method 2: 1 the millennium is calculated from the year x000 - x999 means that from 1000-1999 is the millennium millennium, from 2000-2999 is called millennium 2000.

Method 3: 1 millennium is counted from year x001 - y000, meaning 1st millennium from AD 1 - 1000 AD, 2nd millennium starting from 1001 - 2000, 3rd millennium starting from 2001 - 3000.

According to this calculation, 2020 belongs to the 3rd millennium or 2000 millennium.

**The formula for calculating the century** is simpler than n = 100xn - 99. The first century is from 1/1/1 to 12/31/100, the 2nd century is from 101 and ends in 200.

The 21st century begins on January 1, 2001 and ends on December 31, 2100. 2020 belongs to the 21st century.

**The formula for calculating the decade** is based on two points of view, one idea that a decade begins with a year with the last zero and ends in a year with the last 9, such as the 1980s in the 20th century. 1980-1989, and 2020 of the 20th century of the 21st century.

Another view is that a decade begins with the year with the last number 1 and ends in the year with the last number 0. For example, the 10th decade of the 19th century began from 2011 to 2020, so 2020 is the last year of this decade.

Of course, the calculation of 2020 as the start of a new decade or the final year of a decade does not affect too much life and also depends on the calculation of each person.

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