Counting time: BCE, CE and centuries
Many countries use one shared calendar. Years after year 1 are CE (Common Era, also written AD). Years before it are BCE (Before Common Era, also BC). BCE years count backwards: 500 BCE is earlier than 200 BCE. There is no year 0: 1 BCE is followed by 1 CE.
A century is 100 years. The 1st century CE is years 1–100, so the 18th century is 1701–1800. Quick rule: drop the last two digits and add 1 (1789 → 17 + 1 = 18th). If the year ends in 00, just drop the zeros (1800 → 18th). A millennium is 1,000 years.
Other calendars exist too, for example the Vikram Samvat and Saka calendars in India, or the Islamic and Chinese calendars. Historians convert between them.
The four great periods and their key dates
A common scheme, first made by European historians, uses four periods:
- Antiquity (about 3300 BCE – 476 CE): from the first writing to the end of the Western Roman Empire. Before writing is prehistory.
- Middle Ages (476 – about 1450/1492): kingdoms, religions and trade routes; about a thousand years.
- Early modern period (about 1450/1492 – 1789): printing, ocean voyages, the Renaissance and Reformation, the Scientific Revolution, strong kingdoms, world trade.
- Modern / contemporary period (1789 – today): revolutions, industry, nations, world wars and today's connected world. Some historians call the time after 1945 the contemporary period.
Why 1453 or 1492? Turning points
A border between two periods is a turning point: an event, or group of events, after which life clearly looked different.
- 476: the last Western Roman emperor lost power.
- 1453: Constantinople fell; the Eastern Roman Empire ended, and Greek scholars and books moved west. The printing press was spreading at the same time.
- 1492: Columbus crossed the Atlantic; the Americas, Europe and Africa became linked, changing trade, food and empires.
- 1789: the French Revolution spread ideas of rights and citizenship.
Historians disagree about which date to use. Change happens slowly; one date is a convention that marks a bigger shift.
Other ways to divide time
- Centuries and decades: equal blocks, easy to count, but nothing special has to happen at their edges.
- Dynasties and reigns: China's history is often told dynasty by dynasty (Han, Tang, Song, Ming, Qing); India's by empires (Maurya, Gupta, Mughal).
- Technology ages: Stone, Bronze and Iron Ages, the Industrial Age, the Digital Age. They begin at different times in different places.
- Regional schemes: Indian history is often divided into ancient, medieval and modern, with turning points that differ from Europe's.
So periods depend on the region and on the question you ask. A history of science, of women's lives or of farming may need different borders.
Zooming in: early modern, the long 19th century and since 1945
Early modern period (c. 1450–1789): knowledge spread by print, sailors linked the oceans, science used experiments, and kings built strong states with armies and taxes.
The 'long' 19th century (1789–1914): historians stretch this "century" to 125 years because it has a clear character: from the French Revolution to the First World War. Industry, railways, nation-states, empires, new rights and mass politics grew. The years around 1900 (the turn of the 20th century) mixed fast change with rising tension.
1914–1945: two world wars and a deep economic crisis. Some call 1914–1991 the "short 20th century".
1945 to the present: the United Nations, the end of colonial empires, the Cold War (to 1991), globalisation and the digital age.
Try it: build a timeline
Draw a line on a long strip of paper. Choose a scale (for example 1 cm = 100 years). Mark year 1 and BCE/CE. Place 8 events from your history book and colour the four great periods. Then make a second timeline of your family (1 cm = 1 year) and decide your own periods. In the 3D, step 6 lets you plant flags to check.
Key formulas and definitions
- Century of a CE year = (first digits after removing the last two) + 1; if the year ends in 00, just remove the 00
- Years between two CE dates = later − earlier
- Years between a BCE and a CE date = BCE year + CE year − 1 (no year 0)
- Antiquity → 476 → Middle Ages → 1453/1492 → Early modern → 1789 → Modern
Worked examples
1. In which century is 1492?
Drop the last two digits: 14. Add 1: 15th century.
2. In which century is the year 1900?
It ends in 00, so just drop the zeros: 19th century (1801–1900).
3. How many years from 300 BCE to 200 BCE?
BCE counts backwards, so 300 − 200 = 100 years.
4. How many years from 50 BCE to 50 CE?
50 + 50 − 1 = 99 years, because there is no year 0.
5. Why is the 'long 19th century' 125 years long?
Historians picked the turning points 1789 (French Revolution) and 1914 (First World War) because the time between them shares features, so 1914 − 1789 = 125 years.
6. Place these in the four great periods: building of the Great Pyramid (c. 2560 BCE), printing press (c. 1450), first steam railway (1825).
Great Pyramid → Antiquity; printing press → border of Middle Ages / early modern (often taken as the start of early modern); steam railway → modern period.
Common mistakes
- Saying 1789 is in the 17th century. Add 1: it is the 18th century.
- Forgetting BCE counts backwards: 500 BCE is earlier than 100 BCE.
- Counting a year 0 when finding years between BCE and CE dates.
- Thinking periods are natural facts. They are tools chosen by historians and differ by region.