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Time Zones

Time Zones. Time Zone: region on earth more or less bounded by longitude that has a legally mandated standard time referred to as local time. Time zones meet at the North or South Poles

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Time Zones

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  1. Time Zones

  2. Time Zone: region on earth more or less bounded by longitude that has a legally mandated standard time referred to as local time. • Time zones meet at the North or South Poles • 24 time zones, 24 hours in a day. 360 degrees of longitude divided by 24 (hours in a day) gives us the 15 degrees longitude that increases or decreases hours depending on which way you are traveling. • Increase/gain an hour every 15 degrees eastward. • Decrease/lose an hour every 15 degrees westward

  3. International Date Line: imaginary line on earth’s surface, opposite of the Prime Meridian where the date changes as one travels east or west across it. • Follows the meridian of 180 degrees longitude roughly down the middle of the Pacific Ocean. • The line is necessary so that there is a fixed boundary on the globe where the calendar date resets.

  4. Crossing west results in a day being added (traveler repeats the day west of the line) • Crossing east results in a day being lost (traveler loses a day east of the line, depending on how far you go)

  5. Greenwich Mean Time is the basis of calculating all times. Greenwich is 0 degrees longitude. • Time zones’ boundaries are irregular mainly because of political factors, and so this has been a subject of criticism. • Time zones can be determined by how countries’ and states’ borders are positioned.

  6. Individual zone boundaries are not straight because they are adjusted for the convenience and desires of local populations. • Moreover, some geographically large countries, such as India and China, use only one time zone but other large countries, such as Russia and the United States, have more than one time zone.

  7. Why do we need time zones? • The expansion of transport and communications, as well as trade globalization, during the 19th century created a need for a more unified time-keeping system

  8. What are the United States’ Time Zones? • The United States uses nine standard time zones. From east to west they are Atlantic Standard Time (AST), Eastern Standard Time (EST), Central Standard Time (CST), Mountain Standard Time (MST), Pacific Standard Time (PST), Alaskan Standard Time (AKST), Hawaii-Aleutian Standard Time (HST), Samoa standard time (UTC-11) and Chamorro Standard Time (UTC+10). • The ones you are most familiar with are Eastern, Central, Mountain, & Pacific. • Alaska & Hawaii have their own time zones.

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