Time Zones Time Zones The system of time

Time Zones

Time Zones �The system of time zones has been fixed by international agreement and by laws in individual countries �Most countries adhere to the system �Some exceptions Example: Saudi Arabians use “solar time” Adjust watches daily, setting midnight at time of sundown However, for international dealings they use international time conventions

Division of Time Zones �The earth rotates 360° in 24 hours �About 15° every hour �Therefore, 24 zones of 15° of longitude each �Called Co-ordinated Universal Time (UTC) �Time changes by one hour (ahead or behind) at the borders of time zones

Borders of Time Zones �Time zone divisions are not always followed exactly �Political, Economic or Social reasons Eastern Standard Time Zone and Atlantic Standard Time Zone runs along New Brunswick/Québec border �Not all divisions are a full hour: Newfoundland is ½ hour later, instead of a full hour Also happens in Afghanistan, Iran, India, Myanmar, and Australia

The Prime Meridian �By international agreement, the starting point is 0° which is the Prime Meridian �Time Zone extends 7. 5° both east and west (to make 15°) �Because the earth rotates from west to east, times west of Greenwich are earlier (times east are later) � 12 Noon in Greenwich is 4 hours earlier in Halifax (8 am) and 1 hour later in Paris (1 pm)

Daylight-Saving Time �To take advantage of the early rise and late set of the sun �In Canada, move the clocks ahead 1 hour in Spring and back 1 hour in Fall �In Southern Hemisphere it would be opposite: ahead 1 hour in Fall and back 1 hour in Spring �Not all places in the world use it Places close to the equator have the same sun rise and sun set time all year Some States don’t change (Kansas)

International Date Line �Arbitrarily chosen to separate one day from the next �Convenient location: most unpopulated area of the world (Pacific Ocean) � 180° Longitude (opposite side of the earth from Prime Meridian) �West of International Date Line is one day later �Fly from Vancouver to Hong Kong leaving on Sunday arriving on Tuesday morning after a 13 hour flight �Fly from Hong Kong to Vancouver leaving Monday evening and arriving Monday morning!