As the clocks fall back an hour this weekend, the biannual debate over the efficacy of changing clocks to prioritize evening light for half the year bursts back into life.
According to the Department of Transportation, which oversees national timekeeping, daylight saving time is observed between the second Sunday in March and the first Sunday in November for three reasons: to commute and run evening errands in the daylight, to save energy in the evening, and to prevent crime.
However, many experts disagree with and, in some cases, have debunked these explanations. Those who study the human circadian rhythm and how it relates to the movement of the sun especially argue for staying on standard time, which is observed during the winter months, all year.
“Most of the scientific data indicate that permanent Standard Time would result in improvements to health, safety and economics,” Erik Herzog, a chronobiologist at Washington University in St. Louis, told the Washington Examiner. He runs a laboratory that studies the underlying mechanisms that govern the circadian rhythm. He’s in good company advocating the end of DST, as there are dozens of scientific papers pointing out the harms of shifting the clock for half the year.
When the time zones first came into use by railroad companies in 1883 and then became law in 1918 with the Standard Time Act, “they were designed so that the middle of each time zone observed the sun directly overhead at noon,” Herzog said. The human body is aligned with the sun, so it wakes up easiest with natural light, which such a design more or less affords.
“This alignment is lost when we observe Daylight Saving Time,” Herzog said. “One consequence is that the clock on the wall (social time) reads an hour later so folks tend to need an alarm clock to wake in the dark for work or school.”
“The biggest factor for human health, safety, and economics is probably the number of days when it is still dark at 8am,” he continued. “Living under ST reduces the number of days with dark commutes to school and work compared to DST.”
The realignment that occurs each November shows positive effects that last about three days after the switch, with fewer heart attacks and car crashes, Herzog said.
The opposite occurs in the spring, when numerous studies show health and safety issues increase in the days following the jump forward.
“The chronic effects may last throughout the months of DST because in many people […] the body clock does not adjust to DST social clock time even over months,” according to an article titled “Why Should We Abolish Daylight Saving Time?” in the Journal of Biological Rhythms.
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Other studies have shown that almost no energy is saved during the summer by extending daylight into the evening, as darker mornings tend to cancel out electricity saved later in the day. A report from DOT itself found that electricity use was reduced by only 1%.
DOT’s claims of crime avoidance do seem to hold up, as a 2012 Stanford University study found that “an increase in light during the hour of sunset impacts a number of socially damaging crimes, including robbery, murder, and rape, with a total estimate[d] social cost avoidance of over $550 million per year.”
Remaining on standard time all year is something states and local municipalities can decide on their own terms, as Arizona and Hawaii have. It would require a change to federal law to make DST the local standard. There are 19 other states considering making the change.
But no matter how the social clock is divided, it can’t add more hours of daylight.
