The Prime Meridian is an imaginary line that runs from the north to the south pole and separates the east from the western hemisphere. It is 0 degrees and runs directly through Greenwich in London. The Royal Observatory in Greenwich London is the starting point for all time zones. From here time is calculated. It is called Greenwich Meantime and shows the local time in Greenwich.
Timezones were created so that every country could have midday when the sun is at the highest point in the sky. As there are 24 hours in a day they divided the world into 24 timezones each 15 degrees apart. As you move east from GMT so the time difference goes forward in hours. As you move west from the Prime Meridian the time goes back.
Timezone Web Page You can use the web site or this map to give examples of how time changes as you go through the timezones
Not every country has GMT all year. In the U.K. we have Daylight Savings Time (DST) This means that in the spring we put the clocks forward an hour. This is so we can have more daylight time in the evenings when people want to be doing things outside while the weather is warm rather than in the morning when most people are in bed. The clocks go back to GMT in the autumn so we have more daylight in the mornings. This is because the sun rises late and we don’t need it so much in the evenings as it is cold so most people stay inside.
If you cross over the international date line then not only do the hours change, so does the day. The international date line is on the opposite side to the prime meridian at 180 degrees. It runs through the Pacific Ocean and separates Asia and Oceania from North and South America. If you travel east over the date line then you loose a day. If you travel west over the date line then you gain a day.
The more timezones you travel through the worse the jetlag will be. Travelling from London to Japan (9 timezones) is far worse than travelling from London to South Africa (2 timezones) even though they are similar distances.
Travelling through many timezones can disrupt your body clock. If it is 08.00 in London and you travel to Japan which is 9 hours ahead then though your body clock tells you it is breakfast time it is teatime in Japan. So instead of getting ready for the day, you will be getting ready to wind down for the evening. The affect can cause headaches, tiredness and irritability, which is not good if you have to go to an important business meeting. Many business people pay a lot more for their flight an go business class so they can sleep on the plane and land at their destination refreshed. Research shows that it takes 1 day for each time zone to recover from jet lag and for your body to get into rhythm.
1 What and where is the Prime Meridian? • 2 What is Greenwich Mean Time (GMT)? • 3 What is a time zone? • 4 Why do we have time zones? • 5 How many time zones are there? • 6 What happens to the time as you travel west from GMT and give and example? • What happens to time as you travel east? Give an example. • 8 How many time zones are there in the USA? Give and example of the time difference between New York on the east coast and San Francisco on the west coast. • 9 What is Daylight Savings time (DST) and why do we have it in this country? • 10 How does travelling through time zones affect business people? Give a detailed example. • 11 What and where is the International Date Line? • 12 Give an example of how crossing the International Date Line affects the date.