1. Calendars and the History of Time
WORLD HISTORY READERS
Level 1-①
Calendars and the History of Time

2. The First Calendars
What did the first calendars help farmers and hunters predict?
• When it would rain
• When it would be hot
• When it would be cold

3. The Roman calendar had 10 months with 30 or 31 days each month.
The Early Calendars
What were some early calendars?
The Egyptian calendar
The Babylonian calendar
The Roman calendar
How were these different than our calendars today?
The Babylonian calendar was based on the new moon. It had 12 months, but there were only 29.5 days between each new moon.
The Roman calendar had 10 months with 30 or 31 days each month.
The Egyptian calendar had 12 months, but each month had only 3 weeks with 10 days per week.

4. 24 hours, 7 days a week, 365 days a year
The Julian Calendar
24 hours, 7 days a week, 365 days a year
When was the calendar most of us use today created?
The calendar with 12 months and 365 days was created in 45 BC. It is the Julian calendar created by Julius Caesar.
What did the Julian calendar measure one year by?
The Julian calendar measured exactly when the sun moved north each year over the equator. However, it was inaccurate by 11 minutes.
A Julian calendar

5. The Gregorian Calendar
How and when was the Julian calendar fixed?
In 1582, Pope Gregory XIII suggested that every 400 years, three “leap days” be removed. A leap day is an extra day added to the calendar, every four years for the Julian calendar. Removing a leap day once in every 133 years gave us the Gregorian calendar, the modern calendar many of us use today.
Pope Gregory Xlll ( )

6. No! Time changes depending on which time zone you are in.
Times Around the World
What is it?
These are the standard time zones of the world. Time is measures using hours from Greenwich Mean Time (GMT) based in London.
Is time the same for everyone?
No! Time changes depending on which time zone you are in.

7. Date Formats
How do different countries around the world write the date?
The 1st of July in 2020
In the US,
this date will be written as 7/1/2020.
In the UK,
this date will be written as 1/7/2020.
In Japan,
this date will be written as 2020/7/1.

8. BC and AD What do BC and AD mean?
BC refers to Before Christ, or before the year Jesus Christ was born.
AD refers to Anno Domini (After Christ in Latin).
Anno Domini with a Roman Date
A date with AD in Slovakia

9. Different Systems Which countries use other calendars today?
Thailand uses the Buddhist calendar.
Korea uses both the Gregorian calendar and the Korean lunar calendar.
Iran uses both the Gregorian calendar and the Islamic calendar.
What will the year 2020 be in those calendars?
2020 in the Buddhist calendar will be 2564 BE (Buddhist Era).
2020 in the Korean lunar calendar will be 629, measured from the founding of the Joseon Dynasty.
2020 in the Islamic calendar will be 1441 AH (Anno Hegirae, after the year of the Hijra).

10. Vocabulary farmer n. season n. a person who owns or manages a farm
one of the four periods of the year: spring, summer, autumn, and winter

11. Vocabulary invent v. hunter n.
to create as a product of one's own ingenuity
hunter n.
a person who hunts wild animals for food or in sport

12. Vocabulary leap n. Buddhist n. a large jump
referring to the religious teachings of Buddha

13. Vocabulary inaccurate adj. minute n. not correct, accurate, or true
sixty seconds, the sixtieth part (1/60) of an hour