美国大陆正式引用四个标准时区：1883年11月18日

在美国拥有时区之前，人们在全国旅行时是如何知道时间的呢？在发明铁路之后，人们从甲地要到乙地必须花很长的时间才能到达，当时使用的是「太阳时间」 (sun time) 。当你从东岸要出发到西岸的时候，每隔12英里就必须调慢一分钟，这样你才能一直知道正确的时间。

当人们开始搭乘火车在一天内旅行数百英里，计算时间就成为一个很大的问题。铁路线也必须设立正确的火车抵达与出发时刻表，但是每个城市的时间都不一样，那该怎么办呢？


Before the U.S. had time zones, how did people traveling across the country know what time it was? Until the invention of the railway, it took such a long time to get from one place to another, that local "sun" time could be used. When traveling to the east or to the west, a person would have to change his or her watch by one minute every 12 miles in order to always have the correct time.

When people began traveling hundreds of miles in a day by train, calculating the time became a problem. Railroad lines needed to create schedules for departures and arrivals, but every city had a different time!

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