1. Measuring and Organizing Time
Tools of the Historian
Measuring and Organizing Time

2. Measuring Time
Historians rely on calendars, or dating systems, to measure time.
Cultures used different calendars based on important events in their history.
Julian Calendar Gregorian Calendar
established by Julius Caesar * based on the birth of Jesus
based on the founding of * used by most of the world
Rome today
Used by Western civilization
for over 1000 years

3. Dating Events
The years before the birth of Jesus are known as “B.C.” - “before Christ”.
The years after the birth of Jesus are called
“A.D.” – “anno domini” - Latin meaning “in the year of our Lord.”
B.C. and A.D. are western / Christian oriented. Some historians believe that terms used to date world events should be “neutral”
w/respect to all global regions/religions.
The preferred abbreviations are:
“B.C.E” (before the common era) instead of “B.C.”
“C.E.” (common era) instead of “A.D.”

4. The years between A.D. 1 and A.D. 99 are considered the 1st century.
Periods of History
Historians divide history into blocks of time known as periods, or eras.
A decade = 10 years
A century =100 years
The year is 2012 and we live in the 21st century.
1500 – 1599 / 16th century
/ 17th century
The years between A.D. 1 and A.D. 99 are considered the 1st century.

5. There is NO year “0.”
To date events before the birth of Christ, or “B.C,” historians count backwards from A.D. 1.
The year before A.D. 1 is 1 B.C.
Note that A.D. is written before the date, while B.C. is written following the date.
Some time lines are written with a “c” written before the date; (c B.C.) The “c” stands for “circa” and means “about”. The “c” is used to indicate that the exact date is not known.

6. Use your notes to answer the following questions.
1. How many years is a century?
2. How may years is a decade?
3. How many decades in 1 century?
4. How many decades in 2 centuries?
5. Name the century:
a)1500 – 1599?
b) ?
c) ?
6. Is there a year “0”?”
7. What does “circa” mean?
8. What day came AFTER December 31, 1 B.C.?
9. What year came AFTER 184 B.C.?
10. What does B.C. and A.D. stand for?

7. 1. How many years is a century? 100 2. How may years is a decade? 10
3. How many decades in 1 century? 10
4. How many decades in 2 centuries? 20
5. Name the century:
a)1500 – 1599? 16th
b) ? 17th
c) ? 18th
6. Is there a year “0”?” NO
7. What does “circa” mean? “about”
8. What day came AFTER December 31, 1 B.C.?
January 1, A.D. 1
9. What year came AFTER 184 B.C.? B.C.
10. What does B.C. and A.D. stand for?
Before Christ and “Anno Domini”