Daylight Saving Time: Why Do We Adjust Clocks in March?

Alarm Clock
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On Sunday (March 9), most Americans will lose a precious hour of their weekend to daylight saving time. Except for those who live in Arizona and Hawaii, adjusting clocks forward an hour in March and back an hour in November is a time-honored ritual, but why do we bother to "fall back" and "spring forward?"

Benjamin Franklin first came up with the idea to reset clocks in the summer to conserve energy and take advantage of extra daylight in the evenings. The official practice, however, did not begin until more than a century later.

In May 1916, as fighting intensified during World War I, Germany established daylight saving time in an effort to preserve fuel for the war effort. The rest of Europe followed suit, and daylight saving time was eventually adopted by the United States in 1918.

President Woodrow Wilson wanted to keep daylight saving time even after the war ended, but the idea was contentious — particularly among the country's farmers, who said the adjustments skewed their routines, which were dictated by the sun's natural cycle. As a result, daylight saving time was abolished after the war.

Yet, during World War II, daylight saving time was instituted again, in order to cut back on electricity and save energy for the war. On Feb. 9, 1942, roughly two months after the Japanese attack on Pearl Harbor, President Franklin Roosevelt established daylight saving time year-round, which was dubbed "War Time."

After the war, U.S. states were given the choice of whether they wanted to stick with daylight saving time. But, this free-for-all system, in which many neighboring towns were operating on different time zones, resulted in mass confusion and bewilderment.

In 1966, Congress enacted the Uniform Time Act to establish some order. The federal law stated that if states chose to observe daylight saving time, they must follow a uniform protocol: daylight saving time would begin on the first Sunday of April and end on the last Sunday of October.

In 2007, the Energy Policy Act of 2005 went into effect, which extended daylight saving time in the United States. Daylight saving time now begins on the second Sunday in March and ends on the first Sunday in November.

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Denise Chow
Live Science Contributor

Denise Chow was the assistant managing editor at Live Science before moving to NBC News as a science reporter, where she focuses on general science and climate change. Before joining the Live Science team in 2013, she spent two years as a staff writer for, writing about rocket launches and covering NASA's final three space shuttle missions. A Canadian transplant, Denise has a bachelor's degree from the University of Toronto, and a master's degree in journalism from New York University.