# Time zones: what time is it in London, England, when U.S. kids on the East Coast are getting up for school? To figure that out, it helps to understand time zones.

Suppose you live in Miami, Florida, and get up at 7 a.m. for school. What time is it in London?

Our map gives you the answer--if you know how to use it. The map shows the world's 24 time zones, which begin at the prime meridian, 0[degrees] longitude. (See the dotted line on the map.)

The prime meridian passes through Greenwich (a part of London). So its time zone became known as Greenwich Mean Time. Today's time system is called Coordinated Universal Time (UTC).

When you travel east from the prime meridian, you need to set your watch forward by one hour for each time zone you enter. When traveling west, you must set your watch back one hour for each time zone.

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Reading a time-zone map isn't as hard as it may seem. Look at the color bars at the top and bottom of the map. Each top bar shows the time in that zone when it is 12 noon in London. Each bottom bar tells you how many hours to add or subtract from UTC to calculate the time for that zone. So when it is 7 a.m. in Miami, it is 12 noon in London.

Bends in the Rule

The day of the week changes when you cross the international date line, located at 180[degrees] longitude in the Pacific Ocean. The date just west of the line is one day later than the date just east of the line.

Time zones can be irregular. Some countries, like Iran, observe a time zone that is half an hour different from the standard time zone.

And look at China. It stretches across four time zones, but its government insists that all clocks in China read the same time as in the capital, Beijing!

Questions

1. When the Seattle Seahawks kick off at 1 p.m. at home, what time is that in New York? --

2. If the President speaks at 9 p.m. from the White House, what time is it in Los Angeles? --

3. When a baseball game begins at 7 p.m. in Chicago, Illinois, what time is it in Anchorage, Alaska? --

4. What South American city on the map is in the same time zone as New York City? --

5. If you fly from New York to Paris, how should you set your watch when you land? --

6. A U.S. soldier calls from Baghdad, Iraq, at 11 p.m., Iraq time. What time is it at his home in Miami, Florida? --

7. Each new calendar day begins at the International Date Line, which is based on which line of longitude? --

8. Suppose you fly east from Tokyo, Japan. If you reach the International Date Line at noon on Wednesday, what day is it after you cross the line? --

9. If it is 2 a.m. in Honolulu, Hawaii, what time is it on the International Date Line? --

10. How many time zones does the U.S. have, including Alaska, Hawaii, and U.S. territories? --

1. six

2. 4 p.m.

3. 6 p.m.

4. 4 p.m.

6. When you land, set your watch six hours ahead [later in the day].

7. 3 p.m.

8. 180[degrees]

9. noon on Tuesday

10. 1 a.m.

Lesson 3

GEOSKILLS

Time Zones p. 20

[] Objectives

* Applying basic math skills in a real-world context.

[] Words to Know

* Greenwich mean time [GMT] and coordinated universal time [UTC]: GMT was adopted in 1884. New technology made timekeeping truer to Earth's rotation (the basis for 24-hour days), so UTC was adopted in 1964. For accuracy, it adds a leap second to the year when necessary, making the last minute of June or December 61 seconds long instead of the usual 60.

Through most of history, human beings got by without time standards. That changed with the spread of railroads. The railroad made it possible to travel long distances so quickly that differences in schedules caused confusion. In 1884, delegates from 25 countries met to devise an international standard.

* For more: On the 1884 International Meridian Conference: greenwichmean time.com/info/conference.htm.

[] Keep It Going

Have students plan a round-the-world trip. Then have them figure out at what time, in each place they visit, they would have to make a call in order to reach their parents at home every night at 10:30?

RESOURCES

[] INTERNET

* How Time Works. Includes section on time zones. people.howstuffworks.com/time.htm

* World Time Zones. Time zone maps with current times. worldtimezone.com

[] BOOKSHELF

* Time, Navin Sullivan (Benchmark Books, 2006). Timepieces, time zones, leap years, radiocarbon dating, and other wags we measure time. Grades 4-7.

* A Wrinkle in Time, Madeleine L'Engle (Holtzbrinck Publishers, 2007). Classic children's novel. Also available as audio disk and as a movie version (2004) in DVD or VHS.