A decade is exactly 10 years.
What is a Decade?
A decade is a time unit used to measure 10-year periods. It helps people group events, trends, and milestones into clear blocks of time.
You’ll often see decades used in:
- History — e.g., “the 1990s”
- Culture and fashion — e.g., 80s music, 70s style
- Technology trends — e.g., the 2000s internet boom
- Personal milestones — turning 20, 30, 40, etc.
How Long is a Decade in Years and Days?
| Time Unit | Length |
|---|---|
| Years | 10 years |
| Months (approx.) | 120 months |
| Weeks (approx.) | ~521 weeks |
| Days (standard) | 3,650 days |
| Days (with leap years) | Around 3,652 days |
How Do Decades Start and End?
There are two common approaches:
- Popular usage (easiest):
- 1990s = 1990–1999
- 2020s = 2020–2029
- Strict calendar method:
- Decades run from year ending in 1 to year ending in 0
- Example: 1981–1990
Most modern sources use the popular method, which aligns with how people speak naturally.
Examples of Famous Decades
- 1920s – The Roaring Twenties
- 1960s – Civil rights & cultural revolution
- 1980s – Tech growth and pop culture icons
- 2000s – Rise of the internet era
FAQs
How many years are in a decade?
A decade has 10 years.
What is a decade in simple terms?
A decade is a 10-year period used to group events and time.
How many days are in a decade?
About 3,650–3,652 days, depending on leap years.
How do you calculate the start of a decade?
Most people count decades from years ending in 0 to 9 (e.g., 2020–2029).
How is a decade different from a century?
- Decade: 10 years
- Century: 100 years
Why do people refer to decades like “the 80s” or “the 90s”?
It’s a simple way to describe trends, culture, and events grouped by 10-year intervals.
Are decades important in history?
Yes. Historians, researchers, and writers use decades to analyze patterns and changes over time.
See Also: Why Do We Have Leap Years and When Is the Next One?