Time Zones

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Time Zones
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• in early days everyone set their clocks according
  to the sun - it was noon (1200 p.m.) when the
  sun was at its highest point (its "zenith") in
  the sky
• in larger communities, the military often would
  fire off a gun to signal this occurrence and
  everyone would reset their watches or, they
  would listen for the tolling of the clock in town
  hall

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• because the length of daylight changes a little
  each day with the change in seasons, the length
  of time from solar noon to solar noon is not
  exactly 24 hours
• as commerce developed, and railways and then
  telegraph communication became more widespread,
  this use of solar time became very difficult as
  each town had a slightly different solar time
  (because the sun is not overhead all places at
  the same time)

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• conductors on trains often had ludicriously
  complicated jobs, trying to keep track of the
  correct time in various small communities as they
  tried to keep the trains running on time

http//www.honorpub.com/graphics/time.gif
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• in 1886 the international community adopted a
  series of measures that solved this and other
  vexing navigational problems at a huge conference
  in Berlin (this was when all of Europe was at
  peace - a rare occurrence - an international
  agreement could be possible)

http//www.labcompliance.com/berlin/berlin.jpg
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• a Canadian, Sir Sandford Fleming, devised the
  notion of what became known as "standard time
• it depended on a consistent system of latitude
  and longitude

• latitude was easy - the equator was 0º and math
  determined the rest - but where is the 0º line
  for longitude - it could go anywhere, and
  different countries thought it should be through
  their country

www.arvadesign.ca/narhf/nar01/ NAR01awards_fleming
.html
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• in 1886 the world agreed that it should pass
  through Greenwich, England (outside London) as
  this was where a very important observatory was
  located - this is called the Prime (or "first")
  Meridian of longitude

http//gauss.gge.unb.ca/grads/sunil/homepage/photo
s/greenwich2.gif
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• it was further agreed that the world would be
  divided into 24 equal time zones (as convention
  had 24 hours in a day)

http//www.suffolkcc.gov.uk/transport/graphics/24h
r_clock.gif
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• since the world is round, there would be
  therefore 360º of longitude
• and therefore each time zone would be 15º wide
  (360/24 15)
• in each of these time zones everyone would adopt
  the same time and as you crossed from one time
  zone to another you changed your watch by one
  full hour

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Time Zones
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Time Zones
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• this was a huge improvement on the old system and
  it was quickly adopted
• the agreement also allowed for nations to alter
  the borders of each time zone somewhat so that
  places that have a lot to do with one another
  could be in the same time zone for convenience
  sake
• there were some other variations as well, eg.
  Newfoundland time