Changing clocks to Daylight Saving Time causes acute harms; remaining on DST causes chronic harms. Permanent Standard Time provides the most benefit to health, safety, economy, and environment.

Public Health

Both the change of clocks to DST and the continual observation of DST pose lethal threats to human health. Changing clocks causes acute harms that persist for several days or even several weeks.BerkGiuntellaRoenneberg 2019-08Smith Continually observing DST causes chronic harms that last for months (in the case of seasonal observance) or years without end (in the case of year-round observance). We never fully adjust to DST, we merely sleep less long and less well than we need.CurtisHollidayKalidindiWatson

The abrupt move forward in springtime by one hour is well-known for its shock to body and mind—causing traffic deaths, workplace accidents, lost productivity, and hospitalizations. Incidence of stroke increases 9% upon switching to DST in spring. Incidence of heart attack increases 24 to 50% after switching to DST, and it decreases 21% after returning to Standard Time in autumn.BrueckMichiganPeraltaSandhuWatson

The observance itself of DST causes subtler but greater harms. Healthful sleep is necessary for prosperity and longevity, and it’s biologically regulated by melatonin and cortisol. The body’s natural release of these sleeping and waking hormones is tuned to the setting and rising of the sun. DST postpones both sunset and sunrise on our social clock, which disrupts the body’s hormone balance, and leads people both to stay awake late and to feel a need to sleep late. However, social schedules demand we wake on time regardless of how we feel, and year-round DST would demand we wake before sunrise for roughly half of the year.CBCGiuntellaGuIngrahamLindsayO’Callaghan

DST’s combination of late daylight and pre-sunrise waking robs us of 19 minutes of sleep every night on average.CermakianCurtisGiuntellaRoenneberg 2019-08 Cortisol rhythms advance only two minutes despite clocks being advanced 60 minutes under DST.Roenneberg 2019-08 This creates a “social jet lag”, which is far worse for health than ordinary jet lag, and which never is relieved under year-round DST.BorisenkovClayEBRSFletcherGiuntellaGuHerf 2019JudaMcMillanRoenneberg 2019-08SRBR The body attempts to compensate by sleeping late on non–work days, but the benefits of sleep can’t be stored.BorisenkovGuRoenneberg 2019-08

DST’s chronic lack of sleep increases risks of heart disease, stroke, diabetes, cancer, high blood pressure, obesity, metabolic disorders, personality disorders, unintentional midday sleep, caffeine abuse, alcohol abuse, depression, and suicidality. It harms cognition, productivity, reaction time, stress management, and life expectancy, in both children and adults.BBCBlockBorisenkovCBCCermakianClayCOFCOCrawfordCurtisDaily HiveEBRSGibsonGiuntellaGuHerf 2019Herf 2018HerringIngrahamJinKalidindiKaramaliLindsayMcCoyMeijerMerlineO’CallaghanOglioreRIVMRoenneberg 2019-08SRBRWatsonWhiteZantinge Delaying sunset and sunrise by one hour increases breast and prostate cancer rates by up to 12%, lung and colorectal cancer 14%, liver cancer 21%, stomach cancer 27%, uterine cancer 30%, leukemia 36%, and esophageal cancer 48%.ClayIngrahamHerf 2018Herf 2019 Seasonal depression is more prevalent at northerly latitudes (10% of Seattle, 25% of Alaska), where winter days are unavoidably shorter. This suffering is most effectively relieved by adding light to mornings—not evenings.Herf 2019McCoyRoenneberg 2019-08

Some claim DST may increase exercise. However, the study to back this claim only considered regions that observe summer DST (ignoring those on year-round Standard Time), its gains averaged just two minutes per day (not the full hour the clock gets advanced), and these small gains were seen only in Europe and Australia (with no gains in America). Another study that did compare close regions with different time observations found no increase or decrease in exercise. Furthermore, evening exercise can disrupt sleep, and lack of sleep can increase sports injuries by 70%.CohenHerf 2019KalidindiLivingstonSRBRWatsonZick

Circadian health experts around the world unanimously endorse permanent Standard Time for health, safety, and prosperity as scientific consensus.FletcherJudaKalidindiLindsayOgliore Organizations of note include the Society for Research on Biological Rhythms (representing over 700 researchers from over 40 countries), the Center for Circadian Biology, the Canadian Society for Chronobiology, the European Biological Rhythms Society, the European Sleep Research Society, and the Australasian Chronobiology Society.AckermanCermakianEBRSESRSRoenneberg 2019-06SST

Public Safety

DST risks the lives of commuting children and adults, whether we observe it seasonally or year-round.BBCClay

The springtime switch to DST shocks the human circadian system with a sudden loss of 40 minutes of sleep on average.Barnes This disruption negatively affects reaction times,Medina which causes traffic deaths in the US to spike 17% the Monday after switching to DST.Boynton The increase in road deaths persists at 5.6% the remaining week after switching.Smith The lives of up to 195 motorists and 171 pedestrians are lost due to ”springing forward” each year.Merline

Furthermore, year-round DST would force us to start work or school before sunrise for a third of the year.BlockCBCHerf 2018JudaLindsayMeijer Mornings are the worst time for dark commutes, when grogginess from lack of sleep (19 minutes average lost every night under DST)CermakianCurtisGiuntellaRoenneberg 2019-08 is strongest for walking or busing children, inexperienced teen drivers, and driving adults alike.ClarkHerf 2019 Motor vehicle accidents are the primary cause of accidental death in the US.Smith 70% of all US pedestrian deaths occur under darkness, and 20% of all US pedestrians killed are children.Mercury In 1974, eight kids died on dark winter mornings in just one month of year-round DST in Florida.Downing 2018JenkinsMerline

The National Education Association, the American Federation of Teachers, the National School Boards Association, and the National PTA have all opposed year-round DST, citing children’s safety.AchenbachJenkins


Both switching to DST and remaining on DST have high economic costs, which manifest as stock-market disruption, lost productivity, workplace injuries, healthcare expenses, and overall lower earnings.CBCDaily HiveJinKalidindiWatson

Workplace injuries in US laborers increase 5.7% in the days after moving clocks forward in spring, due to the sudden loss of an average of 40 minutes of sleep. Injuries increase in severity too, resulting in 68% more days lost after switching clocks forward. US office productivity drops 20% after springtime switching, for a loss of $434M annually nationwide. Stocks drop 200 to 500% more than usual the Monday after moving clocks forward to DST, at a cost of $31B in the US. These injuries, missed days, lost productivity, and stock losses don’t reoccur in the autumn return to Standard Time, nor are they ever recouped.BarnesRoenneberg 2019-08Wagner 2014Wagner 2012

Economic losses continue under DST beyond the springtime clock switch, as seen in data from western and eastern edges of time zones, where sunsets and sunrises naturally differ by an hour. One added hour of sunlight in evenings and its corresponding lost hour in mornings reduce sleep duration by an average of 19 minutes nightly.CermakianCurtisRoenneberg 2019-08 This continual loss of sleep every night manifests as health problems (at a cost of $2.35B annually in the US), as lost productivity (totaling 4.4M lost work days, at a cost of $613M annually nationwide), and even as lower earnings (3.0 to 4.9% less than in neighboring counties with a one-hour earlier sunset and sunrise). An increase in average nightly sleep by a full hour can increase earnings by the same amount as half a year of added education would, and it can increase productivity more than an entire year of added education.GibsonGiuntellaIngraham

Energy & Environment

DST wastes energy and increases pollution. Taking an hour of daylight from mornings to add to evenings might reduce evening lighting costs as originally promised, but it’s offset by increased morning lighting, and lighting is no longer even a considerable energy expense. Instead, DST increases demand both for morning heat (since it wakes us before sunrise) and evening air conditioning (since it keeps us awake when solar build-up is strongest). DST also encourages more evening driving, leading the petroleum and retail industries to become major lobbies for extensions of DST. These increases to heating, air conditioning, and driving all increase energy costs, pollution, and global warming. It’s a chief reason why Arizona observes year-round Standard Time.Albeck-RipkaBambrickBlockCohenHandwerkKorchKotchen 2008-10Kotchen 2008-12Porter

When Indiana switched from year-round Standard Time to summertime DST in 2007, annual consumer electricity demand rose 1 to 4%. This jump cost residents an extra $9M per year in utilities, and up to $5.5M annually in added pollution expenses. The same effect was seen in Sydney, Australia, when DST was extended for the 2000 Summer Olympics. Energy waste could be even worse in regions with greater populations or more extreme weather.Albeck-RipkaHandwerkKalidindiKorchKotchen 2008-10Kotchen 2008-12Porter

Religious Freedom

Standard Time is known as God’s time to some, for its proximity to natural (solar) time.KorchMauer DST’s arbitrarily added hour disrupts time-based prayers, which is unfair to many religious communities. Judaism, for example, calls for morning prayers at sunrise, which would overlap with work hours under year-round DST.CohenEllerJTA

Agudath Israel of America, Agudath Israel of California, Agudath Israel of Florida, the Rabbinical Council of America, the Rabbinical Council of California, and Adath Israel of San Francisco have all opposed year-round DST and endorsed year-round Standard Time.EllerJTASST

Late Sunrises

Year-round DST makes sunrises too late. Under year-round DST, sunrise would be as late as 8:40am in North Carolina, 8:44am in California, 8:46am in New York, 8:56am in Texas, 9:01am in Ohio, 9:33am in Michigan, 9:44am in the contiguous US, and 10:04am in British Columbia.Time & Date

Sunrises after 8am DST would last as many as 15 weeks (3.5 months) in California, 15 weeks (3.5 months) in New York, 16 weeks (3.7 months) in North Carolina, 19 weeks (4.3 months) in Ohio, 20 weeks (4.7 months) in Texas, 22 weeks (5.2 months) in Michigan, 24 weeks (5.4 months) in the contiguous US, and 23 weeks (5.2 months) in British Columbia.Time & Date

Public Opinion

Many politicians assume the public prefers DST, but data and history indicate otherwise. Preference between the two times is rarely asked, and polls depend heavily on how and when they’re conducted. Most people don’t know which time is which (granted, it can be confusing). Many who think they prefer DST usually just prefer summer’s naturally longer days, without realizing how dark winter mornings would be under year-round DST.AchenbachHerf 2019MeijerRasmussen

Those who favor one time or the other are generally split (40% Standard vs 31% DST in a 2019-October poll of 1,075 Americans;AP-NORCDavies 35% DST vs 28% Standard in a 2019-March poll of 1,288 Americans;Ballard 47% Standard vs 41% DST in a 2019-February poll of 1,030 Seattleites).Sistek

The majority clearly wish to stop switching clocks as soon as possible (93% in a 2019 poll of 223,273 British Columbians;Crawford 84% in a 2018 poll of 4.6M Europeans;CohenCommissionSchreuerWatson 67% in a 2018 poll of 600 Pacific Northwesterners;PEMCO 60% in California’s 2018 Prop 7 ballot measure;Herf 2019Sheeler 54% in a 2019 poll of 1,288 Americans).Ballard

History has shown when public opinion favors year-round DST before enactment, support quickly reverses to opposition after DST’s long, dark winter mornings are experienced. This happened most clearly in the US in 1974, when support for year-round DST dropped from 79% to 42% in a matter of months. Similar outcomes occurred in the UK in 1971, and in Russia in 2014.BBCHerf 2019Herf 2018LindsayMerlineRipleyYorkshire

Public opinion demands we stop switching clocks now. The quickest, easiest, safest way is to restore year-round Standard Time. Moreover, public health demands we both stop switching clocks now and choose year-round Standard Time. Public health must take precedence over shifting public opinion of the two times.Herf 2019Herf 2018Roenneberg 2019-08

Learn from History

The US tried year-round DST in 1974. While initially supported by an estimated 79% of the population, its popularity quickly plummeted to 42% after its first winter. Several children died on their way to school, the public bemoaned the unnaturally late, dark mornings, and the two-year experiment was ended a year and a half early.ClarkDowning 2005Downing 2018Herf 2019JenkinsMerlineRipleyRoenneberg 2019-08

Year-round DST was similarly tried in the UK from 1968 to 1971, and in Russia from 2011 to 2014. Each time, the program was greeted with initial optimism, followed by public outcry and reversal.BBCHerf 2019Herf 2018LindsayMerlineRoenneberg 2019-08Yorkshire Why waste time, money, and lives repeating bad history?

Objective Reality

No bill can make winter’s daylight as long as summer’s daylight. DST is mistakenly associated with summer’s naturally longer days, but summer days will still be just as long under year-round Standard Time as they were under DST.MeijerRoenneberg 2019-08US Naval

DST is akin to “vanity sizing”, wherein clothiers arbitrarily assign different numbers to the same sizes to make consumers feel thinner. DST’s arbitrarily added hour falsely makes some people feel they have more daylight. We could add six hours to the clock to postpone daylight until a false midnight, but it would then be dark until a false noon.Herf 2019Time & Date

DST leads to an “arms race” against start times. We push clocks forward for more daylight after school/work, then we push start times later for more rest before school/work, which reverses the gain in daylight after school/work.Roenneberg 2019-08 Enactment of year-round DST has been historically followed by enactment of double-DST (pushing clocks forward two hours).CohenKorchYorkshire Calls have begun to delay school until 8:30am,Alexia and to delay work until as late as 10am.Stoneham But without Standard Time as a foundation, the numbers we assign to hours lose meaning. 8:30am DST is 7:30am Standard Time, and 10am DST is only 9am Standard.US Naval The benefits of starting school/work later are threatened by year-round DST and protected by year-round Standard Time.GiuntellaSkeldon

Standard Time is the most practical model for timekeeping that is based in objective reality. It’s an approximation of solar time, which is itself a geometric measurement of nature. Twelve noon corresponds to the sun’s highest point in the sky; twelve midnight corresponds to the darkest point of night. Twelve was chosen for its even fractions (half, third, quarter).US Naval

Standard Time facilitates many simple estimations: time of day from the sun’s position, time of night from the moon or stars, time of sunrise or sunset, time zone differences, latitude on earth, sunburn hours… This knowledge—this connection to nature—is needlessly obscured under Daylight Saving.ChristensenHirsbergKher

Simplest Solution

The simplest way to end clock changes is to restore year-round Standard Time. In both the US and Canada, year-round Standard Time could end clock switches in mere months, with no need for federal action. Arizona, Hawaii, and all US territories did this long ago, and no complaints have been heard since.CravenKorchMauerSkeltonWatson

Pursuit instead for year-round DST would require sweeping change to federal law by Congress—which would take several years, which might never occur, or which might be changed then reverted (as happened in 1974). Year-round DST defies the people’s will for an immediate end to clock switches; it’s a waste of legislative time and taxpayer money.Herf 2019MerlineRipley

A return instead to year-round Standard Time would cost nothing and could be enacted in less than a year. It would benefit public health, public safety, the environment, energy usage, productivity, and wages. It would prove more popular both for its quickness and its lasting approval. It would be an easy win for lawmakers.Herf 2018Roenneberg 2019-08