Daylight Saving Time (or “Summer Time," as it's known in many parts of the world) was created to make better use of the long sunlight hours of the summer. By “springing" clocks forward an hour in March, we move an hour of daylight from the morning to the evening. On the first Sunday in November, we “fall back" and rewind our clocks to return to Standard Time.
The idea was first suggested in an essay by Benjamin Franklin in 1784, and later proposed to British Parliament by Englishman William Willett 1907. However, it did not become a standard practice in the United States until 1966. Daylight Saving Time was originally instituted in the United States during World War I and World War II in order to take advantage of longer daylight hours and save energy for the war production.
In the years after World War II, individual states and communities decided whether they wanted to continue observing Daylight Saving Time and when to do so. This meant some cities were an hour behind others even though they were only separated by a few miles on a map.
Daylight Saving Time is most helpful to those who live farther from the equator, where daylight hours are much longer in the summer than in the winter. In locations closer to the equator, daylight hours and nighttime hours are nearly the same in length throughout the year.
That's why many equatorial cities and countries do not participate in Daylight Saving Time. In the United States, there are only a few places that do not observe Daylight Saving Time, including parts of Arizona, Hawaii, Puerto Rico, the U.S. Virgin Islands and American Samoa.
There are currently about 70 countries that participate in Daylight Saving Time, though not necessarily on the same schedule as the United States. Determining who recognizes Daylight Saving Time and when can sound like a very complicated math word problem.
In Europe, Daylight Saving Time runs from the last Sunday in March through the last Sunday in October. In the southern hemisphere, where the summer season begins in December, Daylight Saving Time is recognized from December through March. Kyrgyzstan and Iceland observe Daylight Saving Time year-round; equatorial countries do not observe Daylight Saving Time at all.
Advocates in support of Daylight Saving Time suggest that in addition to reducing crime and automobile accidents, extended daylight hours also improve energy conservation by allowing people to use less energy to light their businesses and homes. Opposing studies argue the energy saved during Daylight Saving Time is offset by greater energy use during the darker autumn and winter months.