What is chronology?
Chronology means arranging events in the order in which they happened. Chronos is a Greek word for time. A timeline is a line that shows events in this order, with older events on one side and newer events on the other.
Why does order matter? Because history is about cause and effect. Farming had to come before villages. Villages had to come before cities. If we mix up the order, we cannot explain why things changed.
Dates are often approximate
For very old times there are no written records. So many dates carry the word about (or the sign ~). A date like '~6 MYA' means 'roughly 6 million years ago, give or take'. Scholars change such dates when new finds are made.
How we count years: BCE, CE, BP and MYA
CE means Common Era. BCE means Before Common Era. The older labels AD and BC mean the same years.
- In CE, numbers go up as time moves forward: 1 CE, 500 CE, 2026 CE.
- In BCE, numbers go up as we go back: 1 BCE, 500 BCE, 3000 BCE. So 3000 BCE is older.
- There is no year 0. The year after 1 BCE is 1 CE.
For very long ago, years are counted in bigger units:
- BP = Before Present. 'Present' is fixed at 1950 CE. So 10,000 BP is about 8000 BCE.
- MYA = Million Years Ago. 6 MYA = 60 lakh years ago.
Working out gaps
Both dates BCE: subtract (3000 BCE to 1000 BCE = 2000 years). One BCE and one CE: add, then subtract 1 because there is no year 0 (500 BCE to 500 CE = 999 years). In class, many teachers accept 1000 as an approximate answer.
How historians find dates
Stratigraphy (study of soil layers): Dust, mud and rubbish pile up over time. A deeper layer was laid down earlier. So an object in a deeper layer is usually older.
Radiocarbon dating: Living things take in a kind of carbon. After they die, this carbon slowly fades away at a known speed. By measuring how much is left in bone, wood or seeds, scientists estimate age. It works up to about 50,000 years.
Other clues: For older rocks and fossils, scientists use other natural 'clocks' in volcanic rock. For later times, written records, coins and lists of kings give exact years.
Timeline I: 6 MYA to 1 BCE
From ancestors to humans (mostly in Africa)
- ~6 MYA: early human ancestors (hominins) start walking on two legs.
- ~2.6 MYA: first stone tools are made.
- ~1.8 MYA: human ancestors move out of Africa into Asia.
- ~7 lakh to 4 lakh years ago: signs of controlled use of fire.
- ~3 lakh years ago: Homo sapiens (modern humans) appear in Africa, later spreading across the world.
- ~40,000 to 10,000 years ago: cave paintings, finer tools, people reach new continents.
The last 10,000 years
- ~8000 BCE: farming and herding begin in West Asia; soon in other places.
- ~3500 BCE: first cities in southern Mesopotamia.
- ~3200 BCE: writing begins in Mesopotamia; soon after in Egypt.
- ~2600–1900 BCE: Harappan cities in the Indus region.
- ~1600 BCE: Shang kings in China; bronze and writing on bones.
- ~1200 BCE onwards: iron tools spread.
- ~500 BCE: big states and empires in many regions.
Notice how the gaps shrink. Millions of years pass before stone tools, but cities, writing and iron come within a few thousand years.
Key formulas and definitions
- Chronology = arranging events in time order
- CE: bigger number = newer; BCE: bigger number = older
- No year 0: 1 BCE is followed by 1 CE
- BP = before present (present = 1950 CE)
- MYA = million years ago; 1 million = 10 lakh
- Gap, both BCE: bigger − smaller
- Gap, BCE to CE: BCE year + CE year − 1
- Stratigraphy: deeper layer = older
- Radiocarbon: carbon fades at a known speed (up to ~50,000 years)
Worked examples
1. Arrange from oldest to newest: 1200 BCE, 3200 BCE, 500 CE, 8000 BCE.
In BCE the bigger number is older. So: 8000 BCE → 3200 BCE → 1200 BCE → 500 CE.
2. How many years passed from the first cities (3500 BCE) to the start of Harappan mature cities (2600 BCE)?
Both are BCE, so subtract: 3500 − 2600 = 900 years.
3. A seed is dated 10,000 BP. Which year BCE is that, roughly?
BP counts back from 1950 CE. 10,000 − 1950 = 8050. So about 8050 BCE, or roughly 8000 BCE.
4. How many years from 200 BCE to 300 CE?
Add: 200 + 300 = 500. There is no year 0, so subtract 1: 499 years (about 500).
5. In a dig, a copper tool lies in layer 2 and a stone tool in layer 5 (layer 1 is the top). Which is older?
Deeper layers are older. Layer 5 is deeper, so the stone tool is older.
6. 6 MYA written in lakh years?
1 million = 10 lakh. 6 million = 60 lakh years ago.
Common mistakes
- Thinking 1000 BCE is older than 3000 BCE. In BCE, the bigger number is older.
- Adding a year 0 when counting from BCE to CE. There is no year 0.
- Reading BP as 'before 2026'. BP counts back from 1950.
- Thinking early dates are exact. Most dates before writing are approximate and may change with new finds.