Shakespeare cautioned us to "Defer no time, delays have dangerous ends." Does daylight saving time have effects that have escaped our attention? Spend a few minutes with this quiz and see if you're a time bandit or a buffoon.
Although he didn't name it, Benjamin Franklin had the idea for daylight saving time in 1784, while serving as U.S. ambassador to France. His tongue-in-cheek solution to people making better use of daylight hours? Fire a cannon just after daybreak.
It took a global conflict -- World War I -- before any country took the idea of shifting the clocks seriously. Germany adopted daylight saving time rules in 1916 in an effort to preserve its supplies of coal.
Germany took the lead in implementing daylight saving time during World War I, but other countries, including the United States, quickly followed suit. In total, 31 nations began shifting their clocks to make better use of daylight hours and to preserve resources for the war effort.
The energy crisis caused shortages of gasoline in the United States and led to gas rationing and year-round daylight saving time. When the crisis ended in 1974, the U.S. resumed its normal DST schedule.
Two U.S. states -- Arizona and Hawaii -- don't observe time-shifting practices. In Arizona, you can blame the heat. The cost to cool homes an extra hour outweighs the savings that come from turning on lights later. In Hawaii, you can blame location. Because the islands sit close to the equator, the length of summer days is about the same as the length of winter days.
Between 1973 and 1975, the U.S. Department of Transportation conducted a study showing that daylight saving time reduced national electricity usage by roughly 1 percent compared with standard time. It's one of the main reasons the U.S. continues DST today.
Until recently, Indiana observed DST in only 15 of its 90 counties. Then the state passed a law stating that all counties would observe DST beginning in April 2006.
Almost 300 million Americans "spring forward" and "fall back" each year. Globally, the number is much larger because the U.S. is just one of almost 80 countries currently observing DST. According to a 2008 paper by the National Bureau of Economic Research, DST affects 1.6 billion people worldwide.
Because daylight saving time begins in the summer, it's sometimes called summer time. In much of Europe, DST is still known as summer time.
Winston Churchill was a staunch supporter of William Willett and Willett's idea of "summer season time." In 1911, Churchill, then England's home secretary, gave a rousing speech in support of yet another daylight saving time bill introduced into Parliament.
In the Northern Hemisphere, DST starts just before summer begins -- typically between March and April -- and winds up just after summer ends -- between September and November. In the Southern Hemisphere, DST begins between September and November and ends between March and April.
The beginning and ending dates of daylight saving time in the U.S. have changed over the years, but ever since Congress passed the Uniform Time Act in 1966, the changeover time of 2 a.m. has stayed the same.
In the spring, when clocks move forward, the time moves from 1:59:59 to 3:00:00. That's not a typo. The full hour between 2:00:00 and 2:59:59 disappears completely. In the fall, when daylight saving time ends, we get the lost hour back.
DST allows commuters to drive home from work in the daylight, which means, in theory, they see the road better and avoid accidents. In one study, the Department of Transportation estimated that 50 lives were saved and about 2,000 injuries were prevented in March and April of the study years.
One of the biggest misconceptions about daylight saving time is that it helps farmers do their work. On the contrary, farmers have long opposed the practice for how it disrupts their schedules.
The U.S. has changed its DST policies several times over the years. The most recent modification came in 2005 with the Energy Policy Act, which tweaked the start and end dates for daylight saving time.
In 1966, the U.S. passed the Uniform Time Act, which set the beginning and ending of DST, as well as the time when the changeover should occur. Between 1966 and 1986, DST began at 2 a.m. on the last Sunday in April and ended at 2 a.m. on the last Sunday in October.
In recent years, researchers have begun to focus on the impact of daylight saving time on human health. In Germany, biologists specializing in natural physiological rhythms and other cyclical phenomena have shown that our circadian body clocks never adjust to DST.
Some studies have indicated that children's pedestrian deaths were four times higher on Halloween than on any other night of the year. This finding provided some of the impetus to extend DST to the first Sunday in November, which officially took effect in 2007.
GMT doesn't change with the seasons. In countries that observe daylight saving time, the time shift is often expressed in terms of GMT. For example, when the United Kingdom and Ireland switch to British summer time, they are one hour ahead of Greenwich Mean Time (GMT + 1).