Timeline and Sources of History

How dates are written in BCE and CE, how decades, centuries and millennia group time, and how archaeological, written and oral sources tell us about the past.

Key ideas

A timeline marks events in the order they happened, from the earliest on the left to the latest on the right.
BCE years count backwards, so a bigger BCE number is earlier; CE years count forwards.
A source of history is anything that tells us about the past.
Archaeological sources are objects and ruins (pottery, tools, coins, buildings) that archaeologists dig up and study.
Written sources include manuscripts (books written by hand) and travellers’ accounts.
Oral traditions are stories, songs and knowledge passed down by speaking, which matter because many people in the past did not write.
Historians compare several sources and check dates, because one source can be incomplete or one-sided.

Remember

BCE	Before Common Era (counted backwards)
CE	Common Era (counted forwards)
Decade	10 years
Century	100 years (1901–2000 was the 20th century)
Millennium	1,000 years, or 10 centuries
Ordering years	BCE first, biggest BCE number first; then CE from smallest to biggest

Watch out

Putting 300 BCE before 500 BCE: in BCE the bigger number is earlier.
Calling 1901–2000 the 19th century: it is the 20th (the century number is one more than the hundreds).
Thinking only written records count as sources: objects and oral traditions are sources too.

Worked example

Arrange these years in order, earliest first: 973 CE, 752 CE, 168 CE, 2835 BCE.

Working: BCE years first, the biggest BCE number first; then CE years from smallest to biggest

Answer: 2835 BCE, 168 CE, 752 CE, 973 CE