1. Time Zones
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2. Day and Night Rotation: is one complete turn around the Earth’s axis
Rotation causes day and night

3. Rotation The earth rotates at a speed of 1000 miles per hour
It rotates from west to east
Earth's rotational axis points in the same direction relative to the stars, so that the North Pole points towards the star Polaris

4. What is a time zone? Areas sharing the same time
Why do we have time zones?
Areas sharing the same time
There are 24 time zones in the world (same number of hours in a day)
We have time zones so that appropriate times correspond with daylight and night
For example, if we only had 1 time zone in the world it would be dark during the day hours for half of the world
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5. Universal Time Greenwich Mean Time Coordinated Universal Time
Greenwich Mean Time: originally used as the international civil time standard
The basis for civil time used today
Developed in 1967
Last modifications were made in 1972, when scientists accounted for leap seconds

6. Greenwich Time Zone

7. Time Zones in the United States
Alaskan Time Zone
Hawaiian Time Zone
Mountain Time Zone
Pacific Time Zone
Central Time Zone
Eastern Time Zone