Decade (dec)
The decade is ten years, or approximately 315,576,000 seconds based on the Gregorian average year. It is not an SI unit, but it is one of the most natural and widely used groupings of years in human thought. We refer to the 1960s, the 1990s, and the 2020s as cultural and historical shorthand, recognizing that a decade is roughly the span of a significant cultural shift, a generation's formative years, or a long-term policy cycle. The decade is the timescale at which trends in music, fashion, politics, technology, and economics tend to be summarized and discussed.
Definition
One decade equals exactly 10 years. Using the Gregorian average year of 365.2425 days, one decade equals 3,652.425 days, 87,658.2 hours, or 315,576,000 seconds (rounded from 315,569,520).
History
The concept of grouping years in tens is ancient and natural, following from the human tendency to use base-10 counting. The Greek word dekás, meaning a group of ten, gave us decade via Latin decas. However, the use of decades as named cultural periods, where people speak of the characteristics of a specific decade as a whole, is largely a modern phenomenon that developed with mass media in the twentieth century. Early twentieth-century journalism began attaching personality to decades — the Roaring Twenties, the Dirty Thirties — and this habit intensified with the rise of television, popular music, and generational marketing in the post-war era.
Common Uses
Decades are used in historical narration and journalism to characterize periods of change. Economic analysts discuss decade-long business cycles, interest rate trends, and commodity price movements. Climate science tracks temperature records and carbon dioxide levels over decades. Medical research follows patient cohorts for decades to study outcomes of long-term treatments. Urban planning and infrastructure projects are scoped in decades. In popular culture, each decade acquires a personality: the fashion, music, technology, and politics that define it in collective memory.
Did You Know? Facts About Decade
- There is an ongoing debate about when decades begin. Most people consider the 1980s to run from 1980 to 1989, but technically, since there was no year zero, the first decade ran from year 1 to year 10, the second from year 11 to year 20, and so on. By that reckoning, the 2020s technically began on January 1, 2021.
- The term 'decade' is also used in music to describe a group of ten notes or the span of ten scale steps, and in the military to denote a group of ten soldiers.
- The concept of generational decades — Baby Boomers, Generation X, Millennials — evolved from marketing research in the 1980s and 1990s. Each generation is typically defined as spanning 15 to 20 years, straddling one or two calendar decades.
- The 1930s were sometimes called the 'Dirty Thirties' due to the Great Depression and the Dust Bowl. The 1950s are often called the 'Fabulous Fifties' in the United States. The 1960s are universally recognized as a decade of radical cultural change across much of the Western world.
- In chemistry and physics, a decade can also refer to a tenfold change in a quantity, not a period of ten years. A frequency decade is a range from some frequency f to 10f, used in filter and amplifier design.