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Daylight Saving Time (DST), popularly but incorrectly called Daylight Savings Time, is the practice of changing the clocks, throughout an entire nation, in the spring and fall. Many people are familiar with the saying “spring forward, fall back.” This means in the spring, clocks are adjusted forward an hour, resulting in the loss of an hour during the night. In the fall, clocks are adjusted back one hour.
Most of the United States (excluding Arizona and Hawaii, for example) and some other countries around the world adjust their clocks in this manner to gain an additional hour of daylight during the warmer months. In fact, this practice is actually called Summer Time in some countries. The effect is that during Daylight Saving Time, it appears that the sun rises 60 minutes later while also setting later in the day. These changes make the day seem longer, though it hasn’t really changed.
One major benefit of Daylight Saving Time is the reduced need for artificial lighting. Since the daylight seems to last for a longer portion of the time people are usually awake and active, energy bills related to artificial lighting may be reduced. There may also be fewer traffic accidents during Daylight Saving Time. Some people theorize that this clock and daylight change may also have an effect on health and crime rates.
In the United States, the second Sunday of March marks the start of Daylight Saving Time; it begins at 2 AM. In the fall, the clocks are set back an hour on the first Sunday in November; however, this was not always the case. Previously, the hour change came four weeks earlier. The Energy Policy Act of 2005 extended Daylight Saving Time to November. This change is predicted to save a large amount of oil, as businesses generally do not need as much power during the daylight hours.
The timing may be a little different in other parts of the world that observe Daylight Saving Time. Countries in Europe have observed it for quite some time. In 1996, however, the European Union’s European Summer Time became standardized. Its beginning and ending dates differ from those in the United States. Clocks in European countries are moved forward on the last Sunday in March, and they are rolled back on the last Sunday in October.
Daylight Saving Time is handled even differently in the southern hemisphere countries that observe it. There, summer comes in December, so the clocks are typically moved forward in October. Countries very near the equator don’t change their clocks in this manner. The hours of daylight they enjoy are similar in all seasons. As such, there’s not much benefit to shifting the clocks.
I wonder why Arizona doesn't subscribe to DST?