Prepared by: Ng, Rica I. III-6 Beed Time Zone of the World

History of telling time Long before, during the prehistoric times, the rising and setting of the sun probably were the principal means of telling the time. As civilizations developed, more precise time-keeping was required. Early agricultural civilizations in Egypt, Mesopotamia, India, China, England, and Mayan civilizations in the New world, observed the sun and the stars in order to tell time and to keep accurate calendars.

The SOLAR NOON was determined for a location by finding the precise moment a stake cast its shortest shadow. The Romans called this the meridian – the sun’s highest point of the day. Our use of AM which means ante meridian: before noon and PM which means post meridian: after noon was derived from the Roman world.

The system of using local time worked satisfactory until the development during the 19 th century of improved transportation such as railroads, and communication such as telegraphs, problems with the local time became more acute and need for an accurate, reliable standardization of time became more apparent. The railroads stimulated the development of STANDARDIZED TIME SYSTEM.

The relationship of longitude to time was used to set up the time zones that we know today. In 1884, the International Meridian Conference was held in Washington, D.C, to set up a system of time zones. The Earth was divided into 24 longitude. The prime meridian was made the central meridian of its time zone and the precise noon at the prime meridian established the time for all places between 7.5ºeast and 7.5º west of that meridian. This pattern followed around the earth. 1 hr = 15° of longitude.

Greenwich Meridian Time zone The local solar time of the Greenwich meridian was chosen as the standard for the entire system. The time of the Greenwich Meridian Time zone (Universal time or Zulu time) is used for reference, and times to the east or west can be distinguished by comparison with it. Time zones to the west of the prime meridian are said to have slow time and places to the east are on fast time. So a place 90°to the east of the prime meridian would be 6 hours fast, while time in the Pacific Time Zone in the US, whose central meridian is 120°W, is said to be 8 hours slow.

Not all countries has the same time zones, some big countries may have several times accordingly to their political and geographical reasons. Russia is the largest country in the world and it has 9 time zones. The United States of America spreads over 6 time zones including Alaska and Hawaii. Canada has also 6 time zones. Australia has 3 time zones. TRIVIAS

Time zone of the USa

International Date Line The expedition of Magellan from Spain to East Asia was the very first human experience with time change on a global scale which led to the establishment of the International Date Line. Exactly half way around the globe from the Greenwich Meridian is the International Date Line. It is an imaginary line that follows the 180 th meridian, excepts Alaska and Siberia and to keep together some Pacific island groups. At the international date line, we turn our calendar to full day back if we are travelling east and a full day forward if we are traveling west.

When you cross the international date line going from west to east, the day becomes “earlier” (ex. Jan. 2 to Jan. 1); when you move across the line from east to west, the day becomes “later” (ex. Jan 1 to Jan. 2).

Daylight Saving Time Orders all clocks set forward by an hour. This practice was first made by the Germans during the World War one. This practice allows the citizenry to “save” an hour of daylight by extending the daylight period into the usual evening hours, thus reducing the consumption of electricity for lighting. The US began the similar policy in Russia has adopted permanent daylight-saving time. In recent years, Canada, Australia, New Zealand and most nations in western Europe have also adopted daylight-saving time.