Daylight Saving Time
There's a myth that Daylight Saving was a practice adopted to give farmers extra time in the sun to work out in the field. But, that's not really why dozens of countries follow it. Daylight Saving Time (DST) is adopted to reduce electricity usage by extending daylight hours, even thought the efficiency of it is debatable. For eight months out of the year, the US and dozens of other countries follow DST, and for the remaining four months, revert back to standard time in order to take full advantage of the sunlight. On the second Sunday of March at 2 a.m., clocks move forward one hour. Then, on the first Sunday of November at 2 a.m., the clocks turn back an hour. A good way to remember it? The time shifts match the seasons: Clocks "spring" forward an hour in March and "fall" back in November. During summer, the sun is out for longer periods of time, so you can rely on daylight to avoid switching lights on. The clocks revert back to standard time during winter so the sun can rise earlier and the world starts the day off with sunlight -- otherwise some places wouldn't see the sun come up until almost 8:30 a.m.
The current March-November system the US follows began in 2007, but the concept of "saving daylight" is much older. Benjamin Franklin appeared to have first mentioned it in 1784, when he wrote a letter to the editor of the Journal of Paris.
DST wasn't widely used until more than a century later, though. Several countries such as Britain and Germany, implemented DST during WWI to cut artificial lighting use so troops could conserve fuel for the war. US didn't standardize the system until 1966, when it passed the Uniform Time Act. For years, the US observed DST from the first Sunday of April to the last Sunday of October. In 2005, President George W. Bush extended DST an extra four weeks, officially taking effect in 2007.
However, not everyone has opted to follow DST. Only 70 countries around the world "save daylight" every year. In the US, states are not required by law to follow DST -- Hawaii and most of Arizona do not observe it. Other states -- like Florida and California -- are working to observe DST year-round (rather than just between March and November).