Come 2am on Sunday, March 11, daylight saving kicks into effect. Clocks spring forward one hour to 3am, which means grumpy mornings for everyone since we get one hour of precious sleep taken away from us. Every year around this time, the debate as to whether or not daylight saving is a good thing gets revived. (Not so much in November since we get an extra hour of sleep then.) Most of us are familiar with the history of "spring forward, fall back." In the US, DST was first observed in 1918, starting March 31, when the Standard Time Act was established. Since then, there have been numerous changes and adjustments to the duration and scope of DST. The most recent change came in 2007, when DST was moved to the second Sunday of March. Previously, we only sprung forward on the first Sunday of April. Of course, if you’re in the two states that do not observe DST -- Hawaii (because there isn’t a large variation in daylight length all year around) and Arizona (because it gets too hot in the summer, so it’s better for residents to have more cool hours in the night) -- then you have no clock adjustments to worry about. One of the biggest reasons advocates of DST put forth for keeping the tradition is that doing so helps America save energy. The logic goes that more people are up at 5pm than at 6am, so a great deal more oil, electricity and energy are used when it’s dark out in the evening. Thus, lengthening the amount of daylight in the evening would help significantly cut down the evening peak load, which more than offsets the small increase in the early morning load caused by the change. DST also saves lives, according to some studies, because the extra hour of afternoon light helps prevent pedestrian deaths and injuries. The Insurance Institute for Highway Safety, for example, cites research that estimates that during 1987-91, some 900 fatal crashes (727 involving pedestrians and 174 involving vehicle occupants) could have been averted had DST been in effect all year long Also, it is believed that DST helps reduce crime. How so? Criminal activity such as assault and theft are much more likely to occur under the cover of the evening darkness, so DST cuts down the available hours for criminal opportunities. Sure, it’s dark in the morning under DST, but then criminals are probably still in bed then. On the flip side, many question the veracity of claims that DST saves energy. A 2007 study found that California, which like the other 48 DST-implementing states had started DST earlier that year, did not see a reduction in overall electricity consumption. Worse were the results of a 2008 study comparing residential power usage in Indiana before and after it adopted DST in 2006. It turns out that people actually used more electricity with DST because of extra afternoon cooling and morning heating. “Here's the problem with Daylight Saving as an energy-saver: We tend to want our computers and our televisions and our radios when we want them. More importantly, Daylight Saving really pushes Americans out of the house at the end of the day. And when Americans go out of the house, they may go to the ballpark, they may go to the mall, but they don't walk there. They get into their cars,” Michael Downing, author of Spring Forward: The Annual Madness of Daylight Saving Time, told NPR back in 2007. “Daylight Saving increases gasoline consumption, something the petroleum industry has known since 1930,” he surmised. Yes, the chief beneficiaries of DST might be oil and gas companies like Chevron (CVX) or ExxonMobil (XOM) ironically, if Downing is to be believed. Indeed, forget about the pros and cons for DST for you and me; Perhaps the greatest reason for the existence of DST these days is the fact that it provides a boost to the economy. Besides oil companies, the retail sector also gets a big boost from DST, which is why the Chamber of Commerce has historically been the strongest DST lobby. With extra daylight, people are unsurprising more likely to head to retail shops. Downing asserts that it was the candy lobby, whose members include Hershey (HSY) and Tootsie Roll (TR), which pushed hard for the 2007 extension of DST to cover Halloween, because children are much more likely to go out trick or treating in the light. (During a failed 1985 attempt to get this extension, members of the candy industry even entered Senate chambers with candy pumpkins and placed them on each Senator’s seat.) Not all businesses like DST though. If people go out more because of longer hours of light, that means that there are fewer people at home watching television, to the detriment and worry of TV networks. Fox’s (NWS) top-rated program, American Idol, for example, typically plunges in ratings the week after DST is initiated, especially among the coveted 18-49 demographic. Meanwhile, another corporation that is perhaps having some cheeky fun with DST is Apple (AAPL). Geekwire conducted a test on an iPhone 4S where it asked Siri when DST for 2012 begins. She replied, “Daylight savings time starts on March 7, 2012. Set your clocks forward one hour.” I just tried it on my iPhone 4S, and I received the same answer from Siri as well.

 Now, today is obviously not the day DST begins, but we do know why the day might hold some significance for Apple – the company just launched a little something called the new iPad, after all. Siri’s operations are entirely unrelated to the clock in the iPhone 4S, so we’re guessing that this is simply a sly marketing trick on the part of the Cupertino-based company. DST will end this year on Sunday, November 4. Meanwhile, remember to allocate an extra hour of sleep on Saturday night.