time zones

TIME ZONES

History of Time Zones

• Prior to the 19th century time was a local phenomenon.

• Town Clocks were set to Solar Noon and everyone in town set their clocks/watches to this time.

• Railroads created a need for standardized time zones. Schedules based on local times were very confusing.

• In 1878 Canadian Sir Sanford Fleming proposed a system of world time zones that became the system we use today.

11am 1am 2am 3am 4am 5am 6am 7am 8am 9am 10am11am 1pm 2pm 3pm 4pm 5pm 6pm 7pm 8pm 9pm 10pm

Midnight

NO

ON

TIME ZONES ON EARTH

Gre

enw

ich

Mer

idia

n

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SUBTRACT HOURS

15° 15° 15° 15° 15°15°15° 15° 15° 15°15°15°15°15°15°15°15°15°15°15°15°15°

Inte

rnat

ion

al D

ate

Lin

e

15°15°

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SUBTRACT HOURS

Spin, Spin, Spin!

• Quick Check:• If Earth rotates 15°/hour…

How many degrees will Earth have rotated after 3 hours?

15° x 3 = 45°

• THESE LONGITUDE LINES ARE 15° APART.• If it is 2pm2pm in time zone A, what time is it in time zone B?

A

B

2 34

56 7

• If it is 9pm9pm at location X, what time is it at location Y?

Y X

• If it is 11am11am at location W, what time is it at location Z?

W

Z

• If it is 10am10am at location R, what time is it at location T?

RT

The International Date Line

• Fixed, arbitrary boundary on the earth in the Pacific Ocean where the calendar date advances

Rules for Crossing the IDL

• Travelling East: results in one day or 24 hours subtracted. The day is “repeated” to the west of the line.

• Travelling West: results in one day or 24 hours added to the eastern side.

Look at Fiji and Samoa again…

• If it’s 2:23 am Thursday in Tonga…

• …it’s 3:23 am Wednesday in Samoa!(and they’re only 552 miles or 888 km apart!)

Note:Note: Latitude does not effect time zones,although some time zones are not exactly aligned with longitude meridians, so you might encounter the edge of another time zone even if you were to

travel north or south. Reason?

Note:Note: Latitude does not effect time zones…Although some many time zones are not exactly aligned with longitude meridians, so you might encounter the edge of another time zone even

if you were to travel north or south. Reason?

You wouldn’t like it very much if your house and the school were in different time zones!

Usually, the boundaries are shifted a bit to run through areas that don’t influence a large population.

The Regents Exam loves to ask questions about time zones with a

different point of view…

Like a bird flying over the North Pole.

We call this a “Bird’s Eye View”

Looking down from the North Pole:

DARKNESS

Looking down from the North Pole:

If it is 8am at location X, what time is it at location Z?

X

Z

If it is 2pm at location W, what time is it at location Y?

Y

W

Y

Could you label this diagram with: NOON, MIDNIGHT, 6am, 6pm?NOON, MIDNIGHT, 6am, 6pm?

Y

W

Y

Real world applications:• Penelope leaves Africa and returns to Florida after a delightful vacation. If

she leaves at 7pm local time in Africa, if the flight takes 8 hours, what will be the local time in Florida when she lands? If she leaves her wrist watch on local Africa time…what will her wrist watch show the time as when she lands in Florida? Can you make up a crazy question?

Your Mission:• Using your time zone calculators and maps write out a time zone

problem or scenario involving a world traveler.Your traveler must:1. Cross the IDL at least once2. Have at least 7 stops on his/her journey or vacation.3. Ask for times at each stop/location AND the final arrival time for

final destination.Rules:• Be specific and be creative.• Account for travel time, estimate these times if necessary.• Account for how long your traveler stays in any particular location.• Use globes to pick destinations.