Geography
in the
News™
Neal G.
Lineback
WORLD TIME
DIFFERENCES
grees longitude), running through Greenwich, England. Each successive time zone,
east and west, was centered on the next 15
degrees of longitude, or 0, 15, 30, 45, 60
and so on. Since the earth rotates toward
the east relative to the sun, high noon
moves westward. As high noon passes
over the central meridian of a time zone,
its entire time zone (7.5 degrees east and
west of the central meridian) has noon.
Although most of the world adopted
standard time zones, some adjustments
were necessary. For example, when a state
or county was divided into two different
time zones, the boundaries between the
time zones were often gerrymandered, or
arbitrarily moved, to solve the problem.
A few countries, such as Saudi Arabia,
Iran, Afghanistan, India, and Myanmar
(Burma), declined the use of time zones in
favor of some form of local time. The
former Soviet Union and Alaska adopted
the time zones to the east to provide an
extra hour of daylight in the afternoon,
giving them permanent “daylight savings time.” China chose to have all of its
territory in a single time zone, although
its breadth is about the same as the United
States, excluding Alaska and Hawaii.
The United States, including Alaska
IDL
Since the beginning of 2000, we have
been repeatedly and dramatically reminded that new transportation and communication technologies make the world
seem smaller and smaller. Business people
who communicate overseas by email, fax
or telephone quickly realize that the world
does not operate only on American time.
Understanding world time zones is essential to maintaining our increasing international contacts.
Until 1884 most of the world used its
own local time. Each place set its clocks
based on high noon, or when the sun
appeared highest in the
WORLD TIME ZONES
sky on each day. For instance, two towns located 12 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5
a few miles east or west
of one another had local
times a few minutes
apart. Local time was adequate until the railroad
and the telegraph came
along. Printing understandable train schedules
based on local time at
every stop made no
sense.
Because of increasing problems with local
time, an international
congress was assembled Geography in the News 06/07/02
in 1884 to establish standard world time zones.
and Hawaii, has six time zones. From east
The world is divided into 360 degrees of
to west, they are based on the central
longitude, 180 degrees east and 180 demeridians of 75, 90, 105, 120, 135, and 150
grees west of the Prime Meridian, which
degrees west. These time zones are given
passes through Greenwich, England. Longeographic names: Eastern, Central,
gitude lines, or meridians, extend from
Rocky Mountain, Pacific (or West Coast),
pole to pole and measure distances east
Alaskan, and Hawaiian time zones.
and west. Since each day has 24 hours, the
Because the U.S. Eastern Time Zone
congress divided the earth into 24 time
is centered on 75 degrees west, or five
zones, each containing 15 degrees of lontime zones west of the Prime Meridian,
gitude.
Washington’s time is five hours earlier
The first 15-degree time zone was
than London’s (Greenwich Time). In other
centered on the Prime Meridian (0 dewords, if a business call must be made
from Washington to London during working hours, it must be made before noon, or
it won’t reach London before 5 p.m. Since
almost all of Western Europe is one additional time zone east of the Prime Meridian, there is a six-hour difference between
Washington and Paris, Rome or Berlin.
Afghanistan time does not quite conform to International Time Zones, as it is
4 hours and 30 minutes later than Greenwich time. This means that it is 9 hr. 30
minutes later in Afghanistan than in the
U.S. Eastern Time Zone, not considering
Daylight Savings Time. In other words, a
phone call to Kabul from Washington,
DC, at 11.00 p.m. would be received at
9:30 a.m. the following day.
Although the ancient Greek and Roman scholars understood earth-sun relationships, it was not until Magellan’s crew
returned from their circumnavigation of
the earth in 1522 that graphic evidence
materialized of an impending problem.
The ships’ logs (faithfully recorded ships’
diaries) were one day behind. This, of
course, occurred because the ships had
sailed westward around the earth. Little
by little over the three-year-long voyage,
traveling in the direction that high noon
moves, the ships “lost” a day.
The solution to the
lost day was for the
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congress to establish
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the International Date
Line, conveniently located on the 180th meridian in the middle of
the Pacific Ocean. The
Date Line is the line
where new dates on
the calendar begin. For
example, while it may
be Sunday at 2:45 p.m.
immediately to the
east of the line, it will
be Monday at 2:45 p.m.
to the west. All of the
©2002 maps.com
earth to the west of the
Date Line will have
already experienced 2:45 p.m. Sunday.
Understanding world time is essential to carrying on international relations and the knowledge demonstrates a
level of sophistication absolutely necessary in today’s international communications.
And that is Geography in the News.
June 7, 2002. #627.
(This is a revised version of GITN 229,
written in 1992. The author is a geography
professor at Appalachian State University,
Boone, NC)