Time Zones

Time Zones

-A time zone is a region of the Earth that has adopted the same standard time (local time). -Most adjacent time zones are one hour apart (although a few are 30 minutes). -They compute their local time as an offset from Greenwich mean time (GMT).

Time Zone Problem

You are in Denver 37oN Latitude, 105oW longitude On June 13, you board a plane at 10 am to fly 10 hours to Tokyo, Japan (41oN latitude, 135oE longitude) What time and day will you arrive in Japan?

Before people commonly used watches and clocks, they used the sun to keep track of time. Device used was a sun dial

They used local sun time based on: -Earth rotates 15 degrees of longitude in 1 hour -It takes 4 minutes for the Earth to rotate through 1 degree of longitude -In one minute of time, the Earth rotates through 15 minutes of longitude.

International Date Line

When crossing over the date line from E to W, you must add a day. When crossing over the date line from W to E you must subtract a day.

Time Zones 2

Standard time zones can be divided by geometrically subdividing the Earth into 24 wedge shaped sections, bordered by meridians each 15o of longitude apart. Exceptions to this due to geographical practicalities (i.e. political boundaries) or seasonal changes can cause irregularly shaped zones.

Time Zone Problem 2

Step 1: Use only longitude for time: You need to find the difference in longitude: 135oE ---------- 180o---------105oW 45o 75o 45o + 75o = 120o

Time Zone Problems

Note: If minutes are used with degrees and you cross over the International Date Line: 180o 179 o 60' Example: How many degrees and minutes are there between 131o 9' E and the international date line? Solution: 179 o 60' - 131o 9' E = 48o 51'

Time Zone Facts

Russia has the largest number of time zones: 11 USA is tied with Canada for second: 6 time zones Taking into account oversees possessions and territories and possessions, France is the largest with twelve time zones. China is the largest country with only one time zone.

Time Zone Problem 3

Step 2: Figure the difference in time: 120/15 = 8 hours (15: Remember the Earth rotates 15 degrees of longitude in 1 hour)

Time Zone Problem 4

Step 3: What time is it in Tokyo? Going west- subtract, going east- add In this case you are going west: 10 am - 8 hours = 2 am

Time Zone Problem

Step 4: If you cross the International Date Line: Going west- add a day, going east- subtract a day In this case, you were going west= add a day Add flight time of 10 hours Solution: June 14 at 12 noon

Steps to calculate time zone problems

1. Draw a diagram 2. Figure how many degrees of longitude are between the two locations 3. Divide by 15. 4. Subtract hours if going west Add hours if going east 5. If traveling west over the International Date line: Add a day If traveling east over the International Date line: Subtract a day. 6. Add the flight time.

History of Time Zones 2

1876: Canada's Sir Sandford Fleming proposed that the time zones, based on GMT, be used for the entire world. By 1929 most major countries had adopted hourly time zones. Today, all nations have standard time zones but not all are hourly. Newfoundland, India and parts of Australia use half hour deviations.

History of Time Zones

GMT was established in 1675 as an aid to determine longitude at sea by mariners. 1868: New Zealand (then a British colony) officially adopted a standard time based on its longitude 175o00'E. 1870: Charles F. Down proposed a system of 4 time zones in the United States.