Daylight Saving Time (sometimes called Daylight Savings Time) is currently in use in over 70 countries worldwide and affects over a billion people every year. The beginning and end dates vary from one country to another. DST is also the subject of controversy and much debate about its given benefits and possible negative consequences.
DST, as practiced in the U.S., is a one-hour change to the standard time during the “summer” season with the intended purpose of making better use of daylight and conserving energy. Clocks are set ahead one hour when DST starts in the spring. This means that the sunrise and sunset occur one hour later, according to the clock, than standard time. On the first Sunday in November, it is necessary for the clocks to “Fall back” one hour to resume standard time.
President Woodrow Wilson first introduced DST in the U.S. – or “fast time,” in 1918 as a temporary measure to support the war effort during the First World War. The U.S. Congress established the Uniform Time Act of 1966 that stated DST would begin on the last Sunday of April and end on the last Sunday of October each year (however, individual states still had the ability to be exempt from DST by passing a local ordinance). The U.S. Congress subsequently extended DST to a period of ten months in 1974 and eight months in 1975, in hopes to save energy following the 1973 oil embargo. The trial period showed that DST saved the energy equivalent of 10,000 barrels of oil each day, but DST proved to be controversial. Many complained that the dark winter mornings endangered the lives of children going to school. The U.S. changed the DST schedule in 1976 and 1987 and after the introduction of the Energy Policy Act of 2005.
DST proponents argue that moving clocks forward offers advantages in terms of more usable daylight periods for retail sales, tourism, recreation and leisure activities, as well as personal and family time. In addition to claims about reducing energy usage, proponents suggest that extended sunlight can be good for physical and psychological health, increased visibility to reduce traffic incidents and perhaps reducing criminal activity.
There is research which provides reason to believe that DST may reduce traffic accidents. However, some of these beneficial claims are disputed or not as clear cut. For example, energy consumption patterns have appeared to have changed since DST was originally introduced and research findings about DST energy saving benefits is limited and contradictory. Since many of us live our lives on a clock-based schedule (as opposed to farmers, for example, who may follow a solar-based schedule), DST proponents argue that many people prefer the increase in the “daylight” hours at the end of the workday. Nonetheless, controversy about the benefits and unintended negative consequences of DST has swirled about since the very first experiments with DST and continues today.
DST and Health Risks
Of course, the adverse effects for most of us starts with the shortened night’s sleep that inherently occurs with the start of the DST period. A loss of even one hour of “typical pattern” sleep may result in short-term increases of reported “tiredness,” difficulty in awaking, irritability and function performance diminishment. These effects may only occur for a day or two but do have a predictable short-term negative impact on people and performance.
Research indicates that the transitions associated with the start and end of DST do disturb sleep patterns and make people restless at night. This results in sleepiness the next day, even during a "Fall back" period, since when we “Fall Back,” we might have trouble adjusting to going to sleep "later" after the time change. The effect of each DST clock adjustment is (at least) a short-term “jet-lag” desynchronized body clock/time zone misalignment. Since different individuals manage time zone jet lag differently, it is difficult to identify universal impacts. It may still be useful to note that for many people, the time zone switch is disorienting and presents (perhaps idiosyncratic) performance challenges. For most of us, it takes a few days, up to a week, to adjust to the changed time zone in our sleep/awake patterns, alertness levels throughout the day and ability to concentrate or focus.
A report in the Business Insider explains some of the negative dysfunctions resulting from the annual DST shift:
“The impacts of DST are likely related to our body's internal circadian rhythm, the still-slightly-mysterious molecular cycles that regulate when we feel awake and when we feel sleepy, as well as our hunger and hormone production schedules. Light dictates how much melatonin our bodies produce. When it's bright out, we make less. When it's dark, our body ramps up synthesis of this sleep-inducing substance. Just like how jet-lag makes you feel all out of wack, daylight saving time is similar to just scooting one time zone over for a few months. The problems with DST are the worst in the spring, when we've all just lost one hour of sleep. The sun rises later, making it more difficult to wake in the morning. This is because we reset our natural clocks using the light. When out of nowhere (at least to our bodies) these cues change, it causes big confusion. Like anytime you lose sleep, springing forward causes decreases in performance, concentration, and memory common to sleep-deprived individuals, as well as fatigue and daytime sleepiness. Night owls are more bothered by the time changes than morning people. For some, it can take up to three weeks to recover from the sleep schedule changes, according to a 2009 study in the journal Sleep Medicine. For others, it may only take a day to adjust to this new schedule. Some studies are more ominous, though. A 2007 study published in the journal Current Biology suggested that humans never really adjust to DST. The researchers explained that the biological clock is in tune to natural changes in light throughout the seasons, and doesn't respond well to artificial or social changes in the time.”
DST can also affect both one’s body clock and health in longer-term ways. Studies show that there is a 10 percent increase in heart attacks following the twice-annual one-hour time shifts. This was particularly significant in the first three weekdays after the annual “spring forward” clock transition. The body clock itself (circadian rhythm) can be severely disrupted for weeks after each clock shift. Some studies suggest that there may be an increase in suicides following the clock change. A study published in 2008 in the Journal Sleep and Biological Rhythms found an uptick in suicides in Australian men during the first weeks after DST begins.
LiveScience.com notes the DST and health risk connection:
“A team of Swedish researchers conducted a study in 2008 that showed the rate of heart attacks during the first three weekdays following springtime daylight saving time increased by about 5 percent from the average rate during other times of the year. As with workplace injuries, the effect did not arise at the end of daylight saving time in the fall. In the 2008 New England Journal of Medicine article that described this pattern, the researchers attributed the small surge in heart attacks in the springtime to changes in people's sleep patterns. Lack of sleep can release stress hormones that increase inflammation, which can cause more severe complications in people already at risk of having a heart attack.”
“Circadian rhythms tick away throughout the body each day, controlling the release of certain hormones that affect moods, hunger levels, and yearning for sleep. When these rhythms get thrown out of whack, even by just one hour during daylight saving time, the human body notices the difference. For some people, the effects of this change can set off debilitating chronic pain. Cluster headaches, for example — or headaches that cluster within one side of a person's head and can cause excruciating pain for days or weeks at a time — seem to be triggered by changes in circadian rhythms, including during the transitions in and out of daylight saving, the New York Daily News reported.“
DST clock shifts sometimes complicate timekeeping and can disrupt travel, billing, record keeping, medical devices settings, electronic equipment functions and operator sleep/awake patterns. There may also be potential problems with some night shift time card calculations, utilities, etc.
DST's clock shifts create differing levels of technology-human interface complexity challenges. The DST shift requires general public, business and NGO compliance to enact the clock shift. This clock shift can therefore be time-consuming, difficult and in some instances not possible, particularly for mechanical clocks. Changing or failing to change the clocks may result in tardy or outright schedule failures (e.g. showing up an hour late for a meeting) or other clock based errors. Those who live/work across a time zone boundary, especially those with differing clock shift-observance rules, have added complexity and additional potential for complicating errors, mistakes and oversights.
Numerous anecdotal summaries report costly examples of DST shift missed or delayed meetings, missed travel departures, lost scheduled broadcasts, billing system errors and disrupted records management. During an autumn transition from 02:00 to 01:00, a clock reads times from 01:00:00 through 01:59:59 twice, possibly leading to confusion in documentation, billing, sequencing and scheduling for those almost 60 minutes. Changes to DST rules cause problems in existing computer email and calendar programs. On my own MS Outlook email/calendar I am currently unable to schedule anything (not that I really want to do so but if I worked night shift then this could be a minor problem for me) for 2:00 a.m. on March 13, 2016 because the system has an inherent programming block. Starting at 2:00 a.m. Standard Time, the clock resets to 1:00 a.m. Daylight Saving Time and the Outlook calendar is not equipped to manage the temporal dilemma. My (limited) choices are for the 1:00 a.m. hour or the 3:00 a.m. hour but nothing will schedule between 2:00 a.m. and 2:59 a.m.
Peter G. Neumann (1994) wrote in "Computer date and time problems" (Computer-Related Risks. Addison–Wesley) that damage to a German steel facility occurred during a DST transition in 1993, when a computer timing system linked to a radio time-synchronization signal allowed molten steel to cool for one hour less than the required cooling duration, resulting in spattering of molten steel when it was poured. The same sort of problems may occur with other complex systems including medical devices, programmable technology.
Human-Technology interface performance is another area of DST shift concern. The body clock shift may result in groggy or tired machine/equipment operations that increases the risk for errors and failures. One potential adverse effect of daylight saving time may result from the extra part of morning rush hour traffic occurring before dawn and traffic emissions then may cause higher air pollution than would have been created during daylight hours. Research has found that having DST all year round could decrease deaths from traffic accidents even more — saving up to 366 lives, according to a 2004 study in the Journal Accident Analysis & Prevention.
LiveScience.com also calls attention to a possible DST Human-Technology Dysfunctional behavior:
“’Cyberloafing’ — the slang word for surfing the Web for personal entertainment during work hours — may not be as life-threatening as heart attacks and workplace injuries, but it can cost companies thousands of salary wages flushed down the Internet tube. A 2012 Journal of Applied Psychology study found that the incidence of ‘cyberloafing’ significantly increased in more than 200 metropolitan U.S. regions during the first Monday after daylight saving time in the spring, compared with the Mondays directly before and one week after the transition. The team attributed the shift to a lack of sleep and thus lack of workday motivation and focus, but was not able to verify this experimentally.”
DST and Diminished Performance
The annual “spring forward” DST clock shift also appears to result in measurable decreases in work performance, productivity, concentration and general overall health indicators. Increases in measurable fatigue can also lead to accidents in the workplace and in operating machinery, including driving automobiles. Road mishap statistics suggest that there is a “DST Monday bump” in accidents and crashes following the start of DST each spring.
LiveScience.com notes that DST is correlated with diminished performance:
“An increase in car accidents during daylight saving time has been both supported and refuted in the academic literature. The general concept supporting the case, however, is that subtle changes in sleep patterns and circadian rhythms can alter human alertness and, in some cases, might increase the risk of potentially fatal car accidents. Still, one 2010 Journal of Environmental Public Health study that analyzed the number of traffic accidents in Finland one week before and one week after transitions into and out of daylight saving time from 1981 through 2006 found no significant change in the number of accidents during this time period. Another 2010 study published in the Journal of Safety Research found that daylight saving time can actually result in fewer crashes by increasing visibility for drivers in the morning.”
Accidents at work happen more often and are more severe after DST induced springing forward, according to a study published in the Journal of Applied Psychology in 2009. LiveScience.com also explains the increase in workplace accidents and injuries:
“Though this threat may not apply to those who work in the relatively padded confines of carpeted office buildings, others who work at more physically taxing jobs, such as miners, have been shown to experience more frequent and severe workplace injuries at the onset of daylight saving time in the spring. The effect has not been detected at the end of daylight saving time in the fall. The 2009 Journal of Applied Psychology study that came to this conclusion found that mine workers arrived at work with 40 minutes less sleep and experienced 5.7 percent more workplace injuries in the week directly following the springtime daylight saving transition than during any other days of the year. The researchers attribute the injuries to lack of sleep, which might explain why the same effect did not pop up in the fall when workers gained an hour of sleep.”
“All of these impacts have economic costs too. An index from Chmura Economics & Analytics, released last year, suggests that the cost could be up to $434 million in the U.S. alone. That's an added up figure from all of the health and lost productivity mentioned above. Other calculations suggest this cost could be up to $2 billion — just from the 10 minutes twice a year that it takes for every person in the U.S. to change their clocks. (If you calculate 10 minutes per household instead of per person this "opportunity cost" is only $1 billion.) And there's some debate as to how much energy DST actually saves. Analysts at the US Department of Energy found that extending DST by four weeks — an act signed into effect by President Bush in 2005 — saved 1.3 trillion watt-hours of electricity. But regional reports have shown a different perspective. For example, a 2007 report from the California Energy Commission showed that DST had essentially no effect on the state's energy consumption. And a study in Indiana showed that DST actually increased energy demand, presumably because of an increased need for air conditioning.”
DST May Also be Losing Public Support
It may also be helpful to note that DST appears to be losing popular support. According to a Rasmussen Report from 2013, only 37 percent of Americans see the purpose of DST compared to 45 percent the year before. The 2014 Rasmussen Survey – 43 percent say there’s no need for Daylight Saving Time while 36 percent think there's still a need for DST. While this public opinion research alone should not be the sole factor in evaluating the benefits and costs of DST, it may be helpful to note that there is not (currently) overwhelming public demand for DST.
For those of us who study human performance variables, the upcoming “Fall back” clock change marking the end of the 2015 DST is a reminder to think anew about the implications of Daylight Saving Time on people and their performance potential. The annual rituals of clocks “springing forward” and “falling back” may (or may not) achieve substantial economic and/or social benefits. There are numerous questions that ought to be studied further and analyzed in more detail on a large social scale about the unintended dysfunctional consequences of this twice a year time zone jump. Some nations have opted to end the seasonal time switching and have move to a year-round DST clock setting while others have fixed a year round standard time setting.
For those of us who manage or research human performance factors, particularly in mitigating the onset of critical incidents, disasters or emergencies – and ensuring effective management of the ensuing crises, the awareness of the potential DST impacts on our people and processes is worthy of consideration. Where appropriate, we should take steps to ensure continuity and resilience of our people, processes and systems. We should provide the essential adjustments that gives people the best opportunity to succeed at what we have asked them to do.
These issues generally fall into the human factors categories of technical, physical and psychological considerations. There are potential technological work process implications for DST. There may be health and diminished performance risks for DST shifts in both the short-term and long-term analysis. There may be DST implications when considering workplace accidents that may have catastrophic consequences. These consequences may have significant economic costs as well as putting the health, safety and well-being of people at greater risks for less than clear economic and/or social benefits.
Do not forget to set your clocks back (“Fall back”) one hour (to 1:00 a.m.) on Sunday morning November 1st 2015 at 2:00 a.m. Enjoy the extra hour of Halloween party recovery sleep!
Suggested Sources for Further Reading
Images: www.elystandard.co.uk, Firestorm, blogs.wsj.com, Firestorm respectively