「要求」
虽然我们生活在同一星球上，但世界各地所用的时间却不尽相同。宣传委员小王想在本期英语板报中向同学们介绍一下有关时间的知识。他找来一些科普材料，让你据此写一篇板报宣传稿。材料如下：
夏天一些国家将时钟比格林威治平时（G.M.T.）调快一小时。在英国，这称为英国夏令时间（British Summer Time）。它有助于人们充分利用清晨的阳光，而在晚上节约照明用电及燃料。
各国的时间因经度变化而不同。当人们乘船或飞机旅行时，他们就会感到这一点。
假设我们星期一正午从伦敦出发，向西飞。如果我们飞得足够快，以至于一直保持太阳在我们的头顶上，那么当我们飞过加拿大、太平洋、俄罗斯、德国，而后再一次回到伦敦时，时间仍旧是正午。但是那不可能是同一天的正午，因为我们已经随着地球转了一圈。所以我们再次到达伦敦时已是星期二正午。那么，日期在我们旅途中的哪一个地方改变了呢。
在世界地图上我们会看到一条由北至南穿过太平洋的线。这就是国际日期变更线（the International Date Line）。为了避免造成混乱，这条假想线所经的大部分地区都是无人居住的海洋。
「范文」
Time in Our World
In summer the clocks are kept one hour ahead of GMT in some countries. In Britain it is called British Summer Time. It helps people to make the best of early morning sunlight and to save lighting electricity and fuel at night.
Although many countries use one time， time differs from country to country in terms of different longitude. People will be aware of the time difference when they are traveling by sea or by air.
Suppose we set out from London by air at noon on a Monday and fly westwards. Let us also imagine that we fly as fast as the sun， so that it always remains exactly overhead. And when we cross Canada， the Pacific Ocean， Russia， Germany and back to London again， it is still noon， but it can not be noon on the same day because the earth has rotated once and one day has passed. Therefore， we have arrived again in London on Tuesday at noon. Where， on our journey， does the day change from Monday to Tuesday？
A map of the world shows， in the Pacific Ocean， a line running from north to south. It is called the International Date Line. For the most part， this imaginary line passes through ocean areas to avoid confusion that would arise if it runs through the populated land.
「评语」
该文属科普性文章，写起来难度较大。但作者用相对简单的词汇将复杂的意思表达得很清楚，达到了科普宣传的目的。句型的变化使文章行文显得紧凑，同时也为文章增添了生气。