On the second Sunday of March， at 2 a.m.， clocks in most of the United States and many other countries move forward one hour and stay there for nearly eight months in what is called Daylight Saving Time. On the first Sunday of November， at 2 a.m.， clocks fall back an hour to standard time.

每年3月第二个周日的凌晨两点，美国大部分地区和其他许多国家的时钟都会拨快一个小时，然后维持差不多8个月，实行所谓的夏令时（也叫日光节约时制）。到11月第一个周日的凌晨两点，时钟又会调回到标准时间。

The current March to November system that the US follows began in 2007， but the concept of “saving daylight” is much older. Daylight Saving Time has its roots in train schedules， but it was put into practice in Europe and the United States to save fuel and power during World War I， according to the US Department of Transportation’s Bureau of Transportation Statistics.

美国现行的3月至11月夏令时开始于2007年，但“节约日光”的概念却有更久远的历史。美国交通部交通统计局的资料显示，夏令时源自列车时刻表，但将其付诸实施的是第一次世界大战期间的欧洲和美国，目的是节约燃料和电力。

Reasons for Daylight Saving Time

实行夏令时的缘由

The US kept Daylight Saving Time permanent during most of World War II. The idea was put in place to conserve fuel and keep things standard. As the war came to a close in 1945， Gallup asked respondents how we should tell time. Only 17% wanted to keep what was then called “war time” all year.

第二次世界大战期间的大部分时间里，美国一直实行夏令时，旨在节省燃料，保持标准统一。1945年，大战接近尾声，美国民调公司盖洛普就时制问题展开调查，只有17%的受访者表示愿意全年保留当时所谓“战争时间”的制度。

During the energy crisis of the 1970s， we tried permanent Daylight Saving Time again in the winter of 1973–1974. The idea again was to conserve fuel. It was a popular move at the time when President Richard Nixon signed the law in January 1974. But by the end of the month， Florida’s governor had called for the law’s repeal after eight schoolchildren were hit by cars in the dark. Schools across the country delayed start times until the sun came up. By summer， public approval had plummeted1， and in early October Congress voted to switch back to standard time.

20世纪70年代能源危机期间，美国在1973年至1974年的那个冬天再次尝试长期实行夏令时，这次还是为了节省燃料。