Name ________________________
Earth Science
Pd _______
Time Zones
Directions: Use the information below and the following charts to answer the questions.
Why Time Zones?
We measure the day by saying that the sun is at its highest point at 12 o’clock midday. Because the Earth rotates, as it
travels around the sun, one half of the earth is in darkness and one half in light all the time. This brings us to a problem.
If it is midday (12:00pm) where you are, on the opposite side of the earth, it is dark. So what time is it on the opposite
side of the world?
Before time keeping and clocks were invented, people used to know approximately what time it was by watching the
sun. If you look out of the window at different times of the day, you will see that the sun is in a different position each
time you look. Once clocks were invented to keep time during the day, scientists had to devise a system to synchronize
time all over the world.
How Do Time Zones Work?
In the late 1800s, a group of scientists figured out a way to divide the world into different time zones. In order to build
the time zone map, they studied Earth’s movements. As the Earth rotates on its axis, it moves about 15 degrees every
60 minutes. After 24 hours, it has completed a full circle rotation of 360 degrees. The scientists used this information to
divide the planet into 24 sections or time zones. Each time zone is 15 degrees of longitude wide.
The imaginary dividing lines begin at Greenwich, a suburb of London. The primary dividing line of longitude is called the
“prime meridian.” Longitude is the angular distance between a point on any meridian and the prime meridian at
Greenwich. The time at Greenwich is called “Greenwich Mean Time” (GMT). As you move west from Greenwich, every
15-degree section or time zone is an hour earlier than GMT, while each time zone to the east is an hour later.
Examples
Having different time zones means that no matter where you live on the planet, your noon is the middle of the day
when the sun is highest, while midnight is the middle of the night. Let’s take a closer look at how this works. Let’s say
you live in Charlotte, North Carolina, and you have a cousin who lives in Madrid, Spain. Charlotte is five time zones to
the west of Greenwich, which is written as GMT -5. Madrid is 1 section east of Greenwich (GMT +1). This means
Charlotte and Madrid are six time zones apart. When your cousin is eating lunch at noon Madrid time, you are probably
just getting out of bed to get ready for school. This is because at 12:00 P.M. in Madrid, it’s only 6:00 A.M. in Charlotte.
On the other hand, if you wanted to chat with your cousin online after dinner at 6:00 P.M., it would already be midnight
in Madrid!
Name ________________________
Earth Science
Pd _______
World Time Zones
1. How did people measure time of day before the invention of clocks?
2. How many world time zones are there? Why?
3. Approximately, how many degrees is each time zone?
4. Looking at the world map, why are some time zones not perfectly straight?
5. Looking at the United States map, list the four major United States time zones in order from west to
east.
6. If the time is 9:00 A.M. in Detroit, what time is it in:
Chicago___________________ New York City_____________
Los Angeles_______________ Denver____________________
Honolulu_________________
7. If the time in London is 12:00 P.M. GMT, what time is it in:
Chicago ___________________ Paris ___________________
Moscow __________________ Tokyo __________________
Buenos Aires ______________
Name ________________________
Earth Science
Pd _______
8. If the time in Chicago is 12:15 P.M., what time is it in:
Chicago __________________ Paris ____________________
Moscow _________________ Tokyo ___________________
Buenos Aires ______________
9. If it is Tuesday morning west of the International Date Line (eastern hemisphere), then what day is it
east of the International Date Line (western hemisphere)?
10. If it is January 7, 10:00 P.M. in Chicago, what date and time is it in London?
11. If it is October 29, 3:00 A.M. in Sydney, what date and time is it in Chicago?
12. A man living in Honolulu, Hawaii on Tuesday 12:00 P.M. calls his cousin in Tokyo, Japan. What time is
it in Tokyo? What calendar day is it?
Name ________________________
Earth Science
United States Time Zones
Pd _______
Name ________________________
Earth Science
World Time Zones
Pd _______