At some point during my slumber tonight I am going to "lose an hour" of sleep. My scout leader wife was diligently emailing parents of Girl Scout Troop 1343 reminding them to set their clocks forward tonight so that they do not miss the meeting tomorrow. Here in Georgia, Daylight Saving Time(hereafter referred to as DST) starts Sunday, March 12th at 2:00 am and ends at 2:00 am on Sunday, November 5th. If you are interested in where it starts around the world, this website is useful. Professor Josh Durkee of Western Kentucky University suggested DST would be an interesting topic to write about, but I always want to increase science literacy with my discussion. Here are four scientific (and not so scientific) things you need to know about DST.
There is no "s": There is no "s" at the end of Saving though you will certainly hear people refer to it as "savings." It has been suggested that the misuse of the term may evolve from the common usage of the term "savings" in daily vernacular.
The day is not actually longer: You will often hear statements like "the day will be an hour longer tomorrow." The duration of a day is roughly 24 hours. The 24-hour solar day is how long it takes for a location on the earth to rotate under the sun from one point to the exact point. There is also a lunar day that is related to the tidal cycle (two low and high tides every 24 hours and 50 minutes). According to the NOAA ocean services website,
Lunar day is the time it takes for a specific site on the Earth to rotate from an exact point under the moon to the same point under the moon....The lunar day is 50 minutes longer than a solar day because the moon revolves around the Earth in the same direction that the Earth rotates around its axis. So, it takes the Earth an extra 50 minutes to “catch up” to the moon
The length of the day is the same, however, the number of actual "daylight hours" is adjusted. No daylight is actually saved in a physical sense. According to timeanddate.com
Less than 40% of the countries in the world use DST. Some countries use it to make better use of the natural daylight in the evenings. The difference in light is most noticeable in the areas at a certain distance from Earth's equator.
There are scholarly studies of the "Pros and Cons": A study in the New England Journal of Medicine suggested that the "loss" of the hour of sleep during the spring adjustment leads to increased risks of traffic accidents. Ironically, the study also used "savings" rather than "saving" (seriously). Other studies found that during DST, there are fewer fatal crashes because there is more "daylight" during busier evening travel hours. There is even scholarly research on the effects of DST on the human body. A 2008 study found an increase in incidences of acute myocardial infarction during the first three weekdays after the transition to Daylight Saving Time. Many studies have also explored how DST disrupts human circadian clocks.
Scott Craven writes in The Republic
A Nebraska legislator recently introduced a bill to end daylight saving time, citing health problems caused by setting the clock ahead. The state's golf industry teed off, saying the loss of post-work daylight would put it in the weeds.
The stance by the golf industry highlights the perceived value of DST to many industries even as some studies find negative consequences. DST has long been touted as a measure to save energy. During the World Wars, it was used as a temporary measure to save energy. The argument stems back to Benjamin Franklin who proposed the idea in 1784. However the modern implementation came from New Zealander George Vernon Hudson, an entomologist, who suggested a 2-hour shift in 1895. Matthew Kotchen, a professor of economics at Yale University and past deputy assistant secretary for environment and energy at the U.S. Department of the Treasury wrote in the New York Times
daylight saving time exists in the United States and dozens of other countries, affecting more than 1.6 billion people worldwide. The argument..... is that changing the clocks — with a spring forward and fall back — will decrease energy consumption because more sunlight in the evenings will reduce the need for artificial illumination.
He goes on to cite a study that he was a part of that found that the time changes increased residential electricity consumption by a range of 1 to 4 percent in Indiana. They attributed this result to increased demand for heating and cooling. He concluded by stating
readers and policy makers should keep in mind (concerning DST)....there are certainly benefits, but energy savings is not one of them – a tradeoff to acknowledge as we enjoy an extra hour of sunlight on those long summer evenings.
Everyone doesn't use it: In the United States, Arizona and Hawaii do not use DST. The Uniform Time Act of 1966 originally mandated the use of DST but the Energy Policy Act of 2005 allows states and territories to decide on implementation. Arizona cites a consistently hot, arid climate as its rationale for opting out though the Navajo Nation in Arizona does adhere to DST. Hawaii argues that their proximity to the equator limits the variability in sunrises and sunsets.
In the grand scheme of things, DST is not an issue that bothers me too much. I am more concerned these days about "actual" adjustments to our climate system. For now, let me go set the clocks before I forget. And oh by the way, here is a really cool website for calculating sunrise-sunset so that you know how many "hours of daylight" you can expect where you live.
