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pocket watches and clocks to the time of the town - enterprising citizens would offer
their services as mobile clock setters, carrying a watch with the accurate time to adjust
the clocks in customer's homes on a weekly basis. Travel between cities meant having
to change one's pocket watch upon arrival.
However, once railroads began to operate and move people rapidly across great
distances, time became much more critical. In the early years of the railroads, the
schedules were very confusing because each stop was based on a different local time.
The standardization of time was essential to efficient operation of railroads.
In 1878, Canadian Sir Sanford Fleming proposed the system of worldwide time zones
that we use today. He recommended that the world be divided into twenty-four time
zones, each spaced 15 degrees of longitude apart. Since the earth rotates once every
24 hours and there are 360 degrees of longitude, each hour the earth rotates
one-twenty-fourth of a circle or 15° of longitude. Sir Fleming's time zones were
heralded as a brilliant solution to a chaotic problem worldwide.
United States railroad companies began utilizing Fleming's standard time zones on
November 18, 1883. In 1884 an International Prime Meridian Conference was held in
Washington D.C. to standardize time and select the Prime Meridian. The conference
selected the longitude of Greenwich, England as zero degrees longitude and
established the 24 time zones based on the Prime Meridian. Although the time zones
had been established, not all countries switched immediately. Though most U.S. states
began to adhere to the Pacific, Mountain, Central, and Eastern time zones by 1895,
Congress didn't make the use of these time zones mandatory until the Standard Time
Act of 1918.
Today, many countries operate on variations of the time zones proposed by Sir
Fleming. All of China (which should span five time zones) uses a single time zone -
eight hours ahead of Coordinated Universal Time (known by the abbreviation UTC -
based on the time zone running through Greenwich at 0° longitude). Russia adheres to
its designated time zones although the entire country is on permanent Daylight Saving
Time and is an hour ahead of their actual zones. Australia uses three time zones - its
central time zone is a half-hour ahead of its designated time zone. Several countries in
the Middle East and South Asia also utilize half-hour time zones.
Since time zones are based on segments of longitude and lines of longitude narrow at
the poles, scientists working at the North and South Poles simply use UTC time.
Otherwise, Antarctica would be divided into 24 very thin time zones!
Time zones have recently been given standard capital-letter abbreviations as follows:
UTC Coordinated Universal Time
GMT Greenwich Mean Time, defined as UTC
BST British Summer Time, defined as UTC+1 hour
IST Irish Summer Time, defined as UTC+1 hour
WET Western Europe Time, defined as UTC
WEST Western Europe Summer Time, defined as UTC+1 hour
CET Central Europe Time, defined as UTC+1
CEST Central Europe Summer Time, defined as UTC+2
EET Eastern Europe Time, defined as UTC+2
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