MSNBC -- On Sunday, Nov. 4, 2012, right at the 2 a.m. hour, your clocks need to "fall back" one hour. But why, in a world of electric lights and global business, do we still follow the daylight saving time (DST) practice?
As far back as the Roman times, societies have adjusted their clocks based on the amount of daylight during the day. Since the Earth spins on an axis as well as revolves around the sun, different parts of the planet get different amounts of sunlight throughout the year. Certain cities close to the poles, for instance, can have up to a month of darkness due to this effect.
For most locations, however, the difference is more subtle. You may notice the sun rising later in the day, as it gets closer to winter. Due to this effect, it would seem that the daylight comes at a later hour in the day (i.e. rising at 7:30 a.m. instead of 6:30 a.m.) and lasts longer in the day, (i.e. setting at 7:30 p.m. instead of 6:30 p.m.). Adjusting the clocks to match, by either adding or subtracting an hour twice per year, helps make the time in hours consistent with daylight during the day.
The history of organized DST dates back to 1905 when English builder William Willet observed many Londoners sleeping through a beautiful summer morning. He campaigned to get the practice into effect until his death in 1915, yet it wasn’t until 1916 that German forces actually used the practice. The US starting their DST practices in 1918, even though it was heavily debated.
The controversy over DST continues even today. Many farmers and evening entertainment interests, like drive-in movies, have historically opposed the practice, while other industries, especially tourism and sports have been especially supportive due to increased profits. In fact, some reports believe businesses like golf courses add nearly $100 million dollars due to DST.
Besides the economic effects on businesses, DST has also been pushed as having an effect on reducing energy costs. During his time in France, Benjamin Franklin wrote an anonymous letter suggesting Parisians rise early to make use of the earlier sunlight, thereby saving candles. Though most modern societies have moved on from candle light, the idea is similar: by having people wake up earlier during daylight hours (by adjusting their clocks), they’ll also use less electricity because the end of their work day will be closer to the time of darkness.
The energy argument for DST was so respected that the latest change to the practice was direct attempt to try to reduce energy usage. In the Energy Policy Act of 2005, this year’s DST was adjusted to run from March to November. With this new range, clocks were set one hour ahead in March, and will be set back one hour this Sunday, November 4. Both changes are set for 2 a.m. local time.