2 The International Date Line The International Date Line is a line of longitude which follows the 180 degree line and passes through the Pacific Ocean.It does not completely follow 180 degrees, as it zig zags around land masses in the Pacific.The purpose of the IDL is to complete the 24 hour per day cycle and provide the start of a new day.If you cross the IDL traveling eastward you loose a day. If you cross the IDL traveling westward, you add a day.
6 Time ZonesBecause the earth rotates continuously, there are parts of the earth that are facing the sun, and others that are without sun light.This rotation is completed within 24 hours and completes a cycle per each day.Therefore, time is different in different parts of the world. This is dependant on the amount of sunlight being received.
7 Time ZonesFor example, at 12 noon the sun should be directly above your location. With the earth rotating, only parts of the world will have the sun directly above and therefore, receiving noon sunlight.At 12 Noon, the sun would be directly above this house
8 Calculating Time Zone Difference Since the earth rotates around its axis once every 24 hours, there are 24 time zones with 1 hour difference between each time zone.Since the earth rotates 360 degrees in 24 hours, the earth completes a rotation of 15 degrees per hour(360 /24)= 15Therefore, each time zone is 15 degrees
10 Calculating Time Zone Difference To calculate time difference between two locations complete the following:Steps:Find the number of degrees difference between the two locations.Take the number of degrees difference and divide by 15. This will find the number of hours difference between the two locations.Add the number of hours difference if going east. OR Subtract the number of hours difference if going west.
12 Calculating Time Zones Example One:John live in Greenwich, England (0 degrees longitude). He plans to make some long distance call to relatives in the following cities. What time will it be at the following locations when it is 12:00pm in Greenwich?Thunder Bay, Ontario (90 Degrees West)Kamloops, British Columbia (120 Degrees West)Baghdad, Iraq (45 Degrees East)Hong Kong, China (120 Degrees East)