Some people hear ’20th century’ and straight up imagine it means the 2000s. Here’s a breakdown of the centuries and their year ranges.
A century is a period of 100 years.
A millennium is a period of 1,000 years.
The next millennium will begin on January 1, 3001, because the current millennium runs from 2001 to 3000.
The 20th century was not the years 1900 to 1999, as many people casually assume. It was actually 1901 to 2000. The 21st century began on January 1, 2001, and will end on December 31, 2100.
This pattern exists because the calendar started counting from year 1, not year 0.
Notably, the 19th century is associated with industrial expansion, colonial empires, and large-scale social transformation. The 20th century is associated with world wars, decolonisation, and rapid technological changes.
Centuries:
Here are the year ranges for the modern centuries:
1st century: 1–100
2nd century: 101–200
3rd century: 201–300
4th century: 301–400
5th century: 401–500
6th century: 501–600
7th century: 601–700
8th century: 701–800
9th century: 801–900
10th century: 901–1000
11th century: 1001–1100
12th century: 1101–1200
13th century: 1201–1300
14th century: 1301–1400
15th century: 1401–1500
16th century: 1501–1600
17th century: 1601–1700
18th century: 1701–1800
19th century: 1801–1900
20th century: 1901–2000
21st century: 2001–2100
What a Millennium Means
Here are the main millennium ranges:
- 1st millennium BCE: 1000 BCE–1 BCE
- 1st millennium CE: 1–1000
- 2nd millennium CE: 1001–2000
- 3rd millennium CE: 2001–3000
- 4th millennium CE: 3001–4000
The next millennium will begin in 3001 because calendar time is counted from 1, not 0. That means every century and every millennium is one year later.
Why This Matters
Understanding centuries and millennia makes history easier to learn, organise and interpret. A century helps us see patterns over 100 years, while a millennium helps us understand civilisation-level change over 1,000 years.
These time divisions are useful for everything from history lessons to research writing, teaching, and genealogy.
Do you prefer thinking in centuries or in millennia when you study history? Drop a comment or a 👍 if you’ve learnt something new today!