Latitude to Climagraphs Part 2 Time and Time Zones

Historically Time was measured based on some form of solar time to measure the sun at its zenith Railways and communications required more accurate systems (ie the issue of speed necessitated change) Chronometers were developed in the 1700s (18th c.) by John Harrison and allowed accurate timekeeping despite motion and conditions on the oceans – ie longitude The need for a prime meridian from which longitude could be measured became increasingly necessary

One Prime Meridian Various reference points had been used by different countries The economic benefits of an agreed PM became obvious US established 4 zones in 1883 Britain established a zone for GB, Scotland & Wales (1840s) Sandford Fleming was instrumental in the institution of standard time

Sandford Fleming Not just time zones – although missing a train in Ireland seems to have prompted him to work on the problem Influential in promoting the 1884 International Meridian Conference at Wash., DC where the Greenwich Meridian was agreed to British importance in ships and shipping Charts of the British Nautical Almanac (from 1767) Quality of data produced by the Greenwich Observ.

Sandford Fleming Aside from his influence on Standard Time Zones (recommended the standard to the Royal Canadian Institute in 1879) http://bit.ly/LqKZDC , Fleming also: Designed the first Canadian stamp – the three penny Beaver (national animal) stamp of 1851 Surveyed the first RR route across Canada Was the head engineer for most of the Intercolonial and Canadian Pacific Railway

Time Systems Greenwich Mean Time The agreement on the Prime Meridian established GMT and all other locations would be + or – GMT Based on the earth’s rotation - irregular By the 1970s greater accuracy was needed and the UTC (Co-ordinated Universal Time) was developed based on atomic clocks Based on the oscillations of Cesium 133 Military Time, a 24 hour clock system, based on GMT - if the military is not using local time the hour includes the notation ‘Z’ (Zulu)

Time Zones We will work with GMT If it is noon GMT, the time zone to the east will be -1 hour (1 pm) and the time zone to the west will be +1 hour (11 am) The example of +1 hour means that one hour must be added to local time to be the equivalent of GMT Time zones do not change on the 15o multiple but rather at the mid-point between the 15o multiples (at the 7 ½ mark) In other words GMT at Greenwich applies from 0o to 7 ½o East and West

World View of Time Zones

International Date Line http://www.youtube.com/watch?v=hPpWCTHjzQI One way of looking at the time change is that as you are moving to the east it is getting later as you approach a day earlier so that when you pass across the IDL you are one day earlier You, therefore, subtract one day When you cross travelling to the west, you add one day.

Time Zones on a Globe

Time Zones in Canada - Summer

Time Zones in Canada - Winter

Standard Time – Not Used By All Many countries do not use Daylight Saving Time – mostly equatorial or tropical countries Russia covers 12 zones but only uses 9 zones China and Mongolia observe only one time zone Antarctica (US station) uses New Zealand time (+12) – others use their country’s local time Arctic time zones are a matter of convenience – generally UTC/GMT or their institutions time The Space Station uses UTC

The 11 Days That Never Were When people in Great Britain went to sleep on Sept. 2, 1752 they woke up the next morning 12 days later. The next day was Thursday the 14th. The Julian calendar was based on a year of 365 ¼ days. This was inaccurate by 11 ½ minutes/solar year Pope Gregory recognized the problem and introduced the Gregorian calendar (not accepted by many Protestant nations for years/centuries) Although somewhat inelegant, it works, and is inaccurate by only 26 seconds per solar year

Time Zone Problems City ‘A’ and City ‘B’ are 60o apart and City ‘B’ is west of City ‘A’. If the time in City ‘A’ is 11 am, what time is it in City ‘B’? Use a process to determine the answer: Draw a diagram What is the difference in longitude? How many hours difference? Earlier or later? Why?