Before the days of fast travel, each local region fixed its own time. Gradually we recognized that each day has an average length which was then divided into sections. Consequently, the idea of 24 sections called hours has been recognised as an international standard. However, each country marks the time that the sun is highest over their heads by calling it midday, noon or 12 p.m. And as the earth revolves around the sun, midday happens at different times in different countries. So midday in Tokyo precedes Cairo. When international travel started to be commercial with ocean liners shipping people around the world, a time standard needed to be set. For historical reasons, the small village of Greenwich, east of London, UK was the chosen measure. This standard is known as Greenwich Mean Time or GMT, and also Standard Clock Time.  GMT is an imaginary line of longitude against which all international time is measured. For example, it is noon in Tokyo, Japan (TYO) 9 hours before noon at GMT (or in London - LON). So the travel trade says Japan is 9 hours ahead of GMT, or Japan is GMT +9. While on the other side of the line, noon happens later than at GMT. In New York (NYC) noon is 5 hours later than in London so it is 5 hrs behind, or GMT -5. Hint: The three letter codes used here are explained in Unit 2. The world has been roughly segmented (or sliced) into long sections called Time Zones. There are 24 zones in all, indicating the 24 hours the earth turns around the sun. Most countries are entirely in one time zone - some like the USA, Brazil, Russia and Australia are in several time zones. For example, in the USA, there are 5 (excluding Hawaii), so New York on the east coast (Eastern time) is 3 hours ahead of Los Angeles on the west coast (Pacific time). When using travel industry references you will see the plus and minus signs: | Greece: General Information Location Europe | | Time in Greece measured against GMT is 2 hours ahead, or +2.
During 6 months of the summer, starting on 25 March and ending on 28 October, Greece "changes the clocks" and the local time is GMT +3. | Local Time GMT +2 (From 25 Mar to 28 Oct GMT +3)
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