Skill 3 · ages 10-13
Counting time
Centuries, BC and AD, and how many years lie between two dates. There is no year zero, and that changes more than you think.
DraftNot yet reviewed by a historian or history teacher.Why
Historians work with dates. If you misread a century or count wrongly across the start of our era, you put events in the wrong place.
Understand it
Our calendar starts with the year AD 1. The year before is 1 BC: there is no year 0. Before Christ you count backwards: 500 BC is earlier than 50 BC.
A century is a hundred years. Strictly counted, the 1st century runs from year 1 to 100 inclusive, the 14th century from 1301 to 1400 and the 15th century from 1401 to 1500. In everyday speech people often say 'the 15th century' for 1400 to 1499, the 1400s. In Spoor we count strictly.
A handy rule: divide the year by 100 and round up. 1302 divided by 100 is 13.02, rounded up that is 14: the 14th century. A round year like 1500 still belongs to the 15th century.
Years between two dates AD: simply subtract. If you go from BC to AD, add both numbers and subtract 1, because the year 0 does not exist.
No year 0: century = year divided by 100, rounded up; across the start of our era, add and subtract 1.
See it on a source
We work out the centuries and count the years in between.
Which century is 1302 in?Show
In the 14th century (1301 to 1400).
Which century is 57 BC in?Show
In the 1st century BC (100 to 1 BC).
How many years lie between 57 BC and 800?Show
57 + 800 − 1 = 856 years, because there is no year 0.
And between 800 and 1302?Show
1302 − 800 = 502 years.
Pitfalls
Not like this: 1302 is in the 13th century, because it starts with 13.
Like this: The first digits plus one: 1302 belongs to the 14th century, just as 2026 belongs to the 21st.
Not like this: From 10 BC to AD 10 is 20 years.
Like this: It is 19 years: 10 + 10 − 1, because the year 0 is missing.
Not like this: 200 BC comes after 100 BC.
Like this: Before Christ you count backwards: 200 BC is earlier than 100 BC.
Do it
Choose a level. Five right in a row and you can do this.
At the table
In which century was your oldest grandparent born, and in which century will your grandchildren live?