【英语时差8,16】时间之谜--世界通用的时区划分（在线收听）

So, we have devices to mark the passing of time. But what time is it now. Clocks in different parts of the world do not show the same time at the same time. This is because time on Earth is set by the sun's position in the sky above. We all have a twelve o'clock noon each day. Noon is the time the sun is highest in the sky. But when it is twelve o'clock noon where I am, it may be ten o'clock at night where you are. As international communications and travel increased, it became clear that it would be necessary to establish a common time for all parts of the world. In eighteen-eighty-four, an international conference divided the world into twenty-four time areas, or zones. Each zone represents one hour. The astronomical observatory in Greenwich, England, was chosen as the starting point for the time zones. Twelve zones are west of Greenwich. Twelve are east. The time at Greenwich -- as measured by the sun -- is called Universal Time. For many years it was called Greenwich Mean Time.