Presentation on theme: "Time Zones in early days everyone set their clocks according to the sun - it was noon (12:00 p.m.) when the sun was at its highest point (its "zenith")"— Presentation transcript:
in early days everyone set their clocks according to the sun - it was noon (12:00 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
because the length of daylight changes, this would not be exactly 24 hours, from noon to noon as commerce developed and railways and then telegraph communication became more widespread, this use of solar time became very difficult as each town would have a slightly different solar time (because the sun is not overhead all places at the same time)
conductors on trains often had ludicrously complicated jobs, trying to keep track of the correct time in various small communities as they tried to keep the trains running on time
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)
a Canadian, Sir Sandford Fleming, had devised the notion that became known as "standard time", which depended on a consistent system of latitude and longitude latitude was easy - the equator was 0 0 and math determined the rest - but where is the 0 0 line for longitude - it could go anywhere and different countries thought it should be through their country
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 line was called the Prime (or "first") Meridian of longitude it was further agreed that the world would be divided into 24 equal time zones
since the earth is relatively round, there would be 360 0 of longitude and therefore each time zone would be 15 0 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
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
The International Dateline If I could travel around the earth (to the east) in an instant I would cross 24 time zones. Each time I would cross a time zone I would move my clock up one hour. When I get back to where I started I would be one DAY ahead of everyone else!
This happened to a famous explorer by the name of Ferdinand Magellan. In order to correct this problem The International Dateline was created. It is an imaginary line that simply tells travelers to adjust their calendars. If you are traveling east and cross the dateline you go back one day. The dateline is the 180 degree line of longitude, directly opposite the Prime Meridian.