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Writing About Centuries and Decades in Academic Writing
June 9, 2020 | Blog, Learning Center
Writing about centuries and decades can be surprisingly complex. Style guides often offer conflicting rules, and even experienced writers struggle with hyphens, capitalisation, apostrophes, and formatting. This guide simplifies the process and shows you how to refer to historical time periods clearly, accurately, and in line with academic style. Whether you’re writing about the 19th century or the 1990s, you’ll find practical examples, common pitfalls, and tips for consistent usage across your paper.
Cheat sheet
- The 19th century refers to 1801–1900. This can also be described as the 1800s.
- Different style guides have different rules—no universal standard exists.
- Always use numbers for specific years (in 1989).
- Only capitalise centuries if they begin a sentence or appear in a title.
- Do not use apostrophes when writing decades (1990s, not 1990’s).
- Use a hyphen only when a century phrase modifies a noun (twentieth-century artists).
| Century | Years | Century | Years | Century | Years |
|---|---|---|---|---|---|
| 1st century | 1–100 | 8th century | 701–800 | 15th century | 1401–1500 |
| 2nd century | 101–200 | 9th century | 801–900 | 16th century | 1501–1600 |
| 3rd century | 201–300 | 10th century | 901–1000 | 17th century | 1601–1700 |
| 4th century | 301–400 | 11th century | 1001–1100 | 18th century | 1701–1800 |
| 5th century | 401–500 | 12th century | 1101–1200 | 19th century | 1801–1900 |
| 6th century | 501–600 | 13th century | 1201–1300 | 20th century | 1901–2000 |
| 7th century | 601–700 | 14th century | 1301–1400 | 21st century | 2001–2100 |
How is a century defined?
A century is 100 years. For example, 1601–1700 can be called the 1600s or the seventeenth century. This dual naming can cause confusion.
Words or numerals?
Style guides vary:
- Chicago & MLA: Use lower-case words: ninth century, twenty-first century.
- AP & APA: Use numerals above nine: 9th century, 20th century.
Use full words if the century begins a sentence.
Correct: Fifteenth-century painters increasingly embraced the use of perspective.
Incorrect: 15-century painters increasingly embraced the use of perspective.
Always use numerals for specific years:
India gained independence in 1947.
When to capitalise centuries
Correct: Nineteenth-century London was heavily polluted.
Correct: The article ‘Top Inventors of the Twentieth Century’ featured the Wright Brothers.
Correct: The article ‘Top Inventors of the Twentieth Century’ featured the Wright Brothers.
Incorrect: The lute was invented in the late Seventeenth Century.
When to capitalise decades
Use numerals without apostrophes: 1990s not 1990’s.
AP/APA prefer numerals; Chicago/MLA allow words if consistent. For clarity, prefer four-digit numerals:
The 1970s was the decade of disco.
The most popular sitcom of the 1990s was Friends.
Never use the 1900s to refer to the first decade of the 20th century. Instead, write:
The first decade of the 20th century witnessed increasing tension among European nations.
When to use an apostrophe
Correct: Grunge rock was popular in the 1990s.
Correct: The steam engine led to rapid industrialisation in the 1700s and 1800s.
Correct: The steam engine led to rapid industrialisation in the 1700s and 1800s.
Incorrect: Grunge rock was popular in the 1990’s.
Incorrect: The steam engine led to rapid industrialisation in the 1700’s and 1800’s.
Incorrect: The steam engine led to rapid industrialisation in the 1700’s and 1800’s.
Apostrophes are acceptable only in informal contractions: class of ’99.
When to use a hyphen
| Rule | Example |
|---|---|
| Use a hyphen when the phrase acts as a compound adjective | Martin Luther King Jr. was a famous 20th-century activist. |
| Do not use a hyphen when the phrase acts as a noun | The Ming Dynasty rose to power in the fourteenth century. |
| Use a hyphen with the modifier mid (an abbreviation) | mid-nineteenth century, mid-twentieth-century authors |
| Use a hyphen with early or late only if they precede a noun | early-twentieth-century movements artistic movements of the early twentieth century |
Common mistakes
| Incorrect | Correct |
|---|---|
| nineteenth century (used for 1901–2000) | nineteenth century (for 1801–1900) |
| the 1950’s | the 1950s |
| early-16th century | early sixteenth century (as a noun phrase) early-sixteenth-century (as an adjective) |
| 15th century art | 15th-century art |
| Mixing forms: 12th century and twelfth century | Use either consistently: 12th century or twelfth century |
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For further details, consult Garner’s Chicago Guide to Grammar, Usage, and Punctuation.