The sun shines on only half of the Earth's surface because the Earth is a rotating sphere. This means that it is morning, evening, and night at different parts of the world. Each country or a part of the country uses a local time to offset these differences. A region of Earth's surface which uses a single local time is called a Time Zone. There are 24 one-hour time zones around the world. These are arranged in vertical longitudinal bands.
This map displays the standard time zones and the current local time at different places in the world, and is a useful resource and aid for school children, parents, teachers, travelers, and anyone else who wishes to learn about the different time zones.
Universal time and Local time
Local time is the measure of the position of the Sun relative to a locality- a country, city, or a town. Local time varies from place to place on earth. Standard time is the official local time in a country or part of the country. Although time zones are arranged in longitudinal bands, in some places they are skewed and are determined by geographical factors or a country's borders.
Most countries have just one time zone, but some large countries such as Canada, Russia and the USA are split over several time zones. As a result, standard time varies across these countries. The USA has nine standard times; four of the main ones are called- Eastern, Central, Mountain, and Pacific. On the other hand, China, spread out over five time zones, uses one standard time.
Before 1972, the universal time was taken as the local time in Greenwich, England at the Prime Meridian at 0° longitude. Coordinated Universal time (UTC) has replaced Greenwich Mean Time (GMT) as the international reference used to set the local time in each time zone.
The International Dateline
The world uses local times at different countries rather than a single universal time. The international dateline is an imaginary line joining the two Poles that roughly corresponds to the 180° line of longitude, though it zigzags to allow for local geographical considerations. The date in the eastern hemisphere is one day ahead of the date in the western hemisphere. When moving from west to east across the dateline, we go back one day. Similarly, while moving from east to west, we add a day.
Last Updated on : 30/05/2013