This Saturday night (technically Sunday morning) at 2:00AM, we turn the clock back one hour in observance of Daylight Saving Time. In honor of the blessed extra hour of sleep, we've excerpted some helpful info on the subject, courtesy of Live Science.
Why do we still have daylight saving time?
Fewer than 40 percent of the world's countries observe daylight saving time, according to timeanddate.com. However, those that do are taking advantage of the natural daylight in the evenings. That's because the days start to get longer as Earth moves from the winter season to spring and summer, with the longest day of the year on the summer solstice. That's because during the summer, Earth, which revolves around its axis at an angle, is tilted directly toward the sun (at least its top half). [Read more about the science of summer]
Regions farthest away from the equator and closer to the poles get the most benefit from the DST clock change, because there is a more dramatic change in sunlight throughout the seasons.
Research has also suggested that with more daylight in the evenings, there are fewer traffic accidents, as there are fewer cars on the road when it's dark outside. More daylight also could mean more outdoor exercise (or exercise at all) for full-time workers.
The nominal reason for daylight saving time has long been to save energy. The time change was first instituted in the United States during World War I, and then reinstituted again during World War II, as a part of the war effort. During the Arab oil embargo, when Arab members of the Organization of Petroleum Exporting Countries (OPEC) stopped selling petroleum to the United States, Congress even enacted a trial period of year-round daylight saving time in an attempt to save energy. [5 Crazy Chapters in the History of Daylight Saving Time]
But the evidence for energy savings is slim. Brighter evenings may save on electric lighting, said Stanton Hadley, a senior researcher at Oak Ridge National Laboratory who helped prepare a report to Congress on extended daylight saving time in 2007. But lights have become increasingly efficient, Hadley said, so lighting is responsible for a smaller chunk of total energy consumption than it was a few decades ago. Heating and cooling probably matter more, and some places may need air-conditioning for the longer, hotter evenings of summer daylight saving time.
Hadley and his colleagues found that the four weeks of extra daylight saving time that went into effect in the United States in 2007 did save some energy, about half of a percent of what would have otherwise been used on each of those days. However, Hadley said, the effect of the entire months-long stretch of daylight saving could very well have the opposite effect. A 1998 study in Indiana before and after implementation of daylight saving time in some counties found a small increase in residential energy usage. Temporary changes in Australia's daylight saving timing for the summer Olympics of 2000 also failed to save any energy, a 2007 study found.
Part of the trouble with estimating the effect of daylight saving time on energy consumption is that there are so few changes to the policy, making before-and-after comparisons tricky, Hadley told Live Science. The 2007 extension of daylight saving time allowed for a before-and-after comparison of only a few weeks' time. The changes in Indiana and Australia were geographically limited.
Ultimately, Hadley said, the energy question probably isn't the real reason the United States sticks with daylight saving time, anyway.
"In the vast scheme of things, the energy saving is not the big driver," he said. "It's people wanting to take advantage of that light time in the evening."
Myths and Interesting Facts about Daylight Saving Time
- Turns out, people tend to have more heart attacks on the Monday following the "spring forward" switch to daylight saving time. Researchers reporting in 2014 in the journal Open Heart, found that heart attacks increased 24 percent on that Monday, compared with the daily average number for the weeks surrounding the start of DST.
- Before the Uniform Time Act was passed in the United States, there was a period in which anyplace could or could not observe DST, leading to chaos. For instance, if one took a 35-mile bus ride from Moundsville, West Virginia, to Steubenville, Ohio, he or she would pass through no fewer than seven time changes, according to Prerau. At some point, Minneapolis and St. Paul were on different clocks.
- A study published in 2009 in the Journal of Applied Psychologyshowed that during the week following the "spring forward" into DST, mine workers got 40 minutes less sleep and had 5.7 percent more workplace injuries than they did during any other days of the year.
- Pets notice the time change, as well. Since humans set the routines for their fluffy loved ones, dogs and cats living indoors and even cows are disrupted when, say, you bring their food an hour late or come to milk them later than usual, according to Alison Holdhus-Small, a research assistant at CSIRO Livestock Industries, an Australia-based research and development organization.
- The fact that the time changes at 2 a.m. at least in the U.S., may have to do with practicality. For instance, it's late enough that most people are home from outings and setting the clock back an hour won't switch the date to "yesterday." In addition, it's early enough not to affect early shift workers and early churchgoers, according to the WebExhibits, an online museum.
Now that you know what it's all about, you can rest easier...especially with an extra hour of sleep. Enjoy!