16-Unit3 Part4.mp3: Part IV More about the topic:Day-light-saving Time As international communications and travel increased, it became clear thatit would be necessary to establish a common time for all parts of the world. In1884, and international conference divided the world into 24 time areas. Eachzone represents one hour. The astronomical observatory in Greenwich England was chosen as the starting point for the time areas. Twelve areas are west of Greenwich; twelve areeast. The time at Greenwichas measured by the sun is called universal time. The following short passage is aboutday-light-saving time. Supply the missing words while listening. Standard time is a worldwide 1) system of time areasbased on longitude. Longitude is the distance on the earth 2) measuring east or west of the first longitude3) line at Greenwich, England. Each time area is 4) 15 degrees longitude wide. Under standard time, the time kept ineach time area is that of its 5) central longitude line. Theselines are 15 degrees, 6) 30 degrees and so on east or west of the 7) first line in England. The 8) difference in time between each nearby area is exactly 9) one hour . All clocks keep the 10) same time within eacharea. In the summer, most people in the United States move their clocks 11) ahead one hour to use day-light-saving time. The only 12) states which do not are Hawaii, Arizona and most of Indiana. Some13) border areas of Indiana keep the same time as 14) nearby states and do change to day-light-saving time. The useof day-light-saving time provides an 15) added hour of day lightin the early evening. Its chief 16) purpose is to save energyby reducing the evening use of 17) electricity forreading. Many countries first used day-light-saving time during 18) war time. For example, Britain went on day-light time during19) WWI , so did the United States. The United States alsoobserved it during 20) WWII .