Supporters of year-round daylight saving time (DST) have traditionally touted energy savings, but permanent DST is also being prescribed as a tonic for the tourism industry.
The tourism argument is that extra daylight in the evening hours would make people more likely to visit parks and other attractions.
"In a nutshell, it would extend the spring and fall shoulder seasons for the tourism industry," said Kurt Janson, policy director at the Tourism Alliance, a lead organization in the United Kingdom's Campaign for Daylight Saving. "There would be more usable daylight in the evening hours, when people are out and about and attractions are open."
The coalition is advocating a three-year trial of year-round daylight saving across the U.K., and the government is currently considering a bill to that effect. Daylight saving time for 2011 ended in the U.K. on October 30.
Janson cited time-use studies suggesting that most visits to parks, attractions and National Trust sites take place in the afternoon after other commitments such as work. "In spring and fall that extra hour of daylight in the evening has a much larger impact on people's ability to quit work and do something."
Janson said these benefits are anticipated by research from the independent Policy Studies Institute, which suggests that the U.K. tourism industry could experience a boost of 3.5 billion pounds (about 5.6 billion U.S. dollars) per year under permanent daylight saving time.
Hendrik Wolff, an environmental economist at the University of Washington in Seattle, said that assertion makes sense, considering daylight saving has been shown to increase active and outdoor activities at the expense of sedentary pursuits like watching television.
"If in the spring and fall, instead of having one daylight hour in the morning and one in the evening, you had zero in the morning but two hours of daylight after work, that covers the fixed time costs of people engaging in outdoor recreation."
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Some Losers If Daylight Saving Were Permanent
Wolff also noted that some seasonal businesses actually open for the spring and summer when daylight saving time starts. "Those businesses may even be able to open a couple of weeks earlier."
"But along with winners, there will likely be some losers," he added. "Indoor recreational behavior, theaters for example, may be at a disadvantage with year-round daylight saving, while outdoor recreation facilities, like a golf course, would stand to benefit."
Some of Australia's provincial governments have also debated extended daylight saving time with an eye toward tourism and recreation, and at least one U.S. state has also explored the option.
Colorado Senator Greg Brophy introduced a bill last spring to place his state on year-round daylight saving time, noting that Colorado's outdoorsy population would appreciate an extra hour in the evening. But at least one large sector of the state's tourism economy wasn't enthused.
Colorado ski resorts opposed the now-failed bill because of concerns that an extra hour of darkness in the morning would prevent patrollers from performing avalanche control and readying the slopes—likely cutting an hour off daily operations.
Daylight Saving Energy Gains Real or Imagined?
Historically, the prospect of energy savings drove widespread embrace of daylight savings.
For example, DST has been extended during crises such as World War II and the Arab oil embargo. "That's why in many countries you still see that it's the energy legislation that determines the start and end dates for daylight saving," said the University of Washington's Wolff.
(Related: "Extended Daylight Saving Time Not an Energy Saver?")
But Wolff points to a body of evidence, including his own work, suggesting that daylight saving time may not really conserve energy at all. In fact, in some regions, DST could actually cause the consumption of more energy.
Wolff co-authored an Australian power study that compared energy use when parts of the nation observed extended daylight saving time for the 2000 Sydney Olympics but others did not.
"We rejected the energy-saving hypothesis," he said, explaining that while electricity use dipped during the lighter evenings those gains were wiped out by increased power demands in the darker morning hours.
Similarly, University of California economist Matthew Kotchen's study compared energy use in Indiana before and after the entire state adopted daylight saving time in 2006. "Because of increased (heating and air conditioning use) they actually found higher energy use with the switch to DST, and not energy savings," said Wolff of Kotchen's 2008 National Bureau of Economic Research study (PDF). The research showed Hoosier state electric bills rose more than $7 million a year under DST.
Results Vary By Region
The verdict on energy savings isn't unanimous. Other studies do suggest that energy gains can be had under daylight saving time—at least in some places.
U.S. Department of Energy analyst Jeff Dowd was lead author of an October 2008 daylight saving time report to Congress (PDF). The study was mandated by the same 2005 energy act that extended U.S. daylight saving time an extra month, to begin on the second Sunday in March and end on the first Sunday in November.
The DOE report found that extended daylight saving time reduced annual U.S. electricity consumption by about half a percent during each day of extended DST. Though that percentage is small, it represents real savings because overall U.S. consumption is so enormous.
Dowd said the same findings might not apply to year-round daylight saving time, however. "Because the energy savings estimates for the DST extension considered in the 2008 DOE study seemed to vary by both region and season we cannot supply an educated guess as to the overall impact of year-round DST," he said.
Regional variations due to differences in climate might also mean permanent daylight saving time could conserve energy in some areas but not as much in others. "The DOE study concluded that the gains were smaller in the South than in the North, likely due to increased air conditioning effect," Dowd said.
Wolff, one of the scholars who contributed to the report, said the results were subject to statistical interpretation and, in his view, went so far as to show that the South is actually a net energy loser under daylight saving time.
The Human Health Arguments
Energy conservation and potential tourism boosts are not the only reasons that year-round daylight saving has garnered some support.
Proponents say it could make roadways safer during the afternoon rush hours when they are frequented by schoolchildren and tired commuters. Boosters also cite benefits to human health, driven largely by the prospect of people becoming more physically active for longer periods of the year.
Some opponents of daylight saving time include the agricultural community, where the loss of early morning daylight is a concern. And those who promote DST-driven road safety in the evenings are countered by those who fear increased dangers to schoolchildren and others traveling in the wee hours if it is still dark outside.
Even human health benefits aren't easy to evaluate. Till Roenneberg, a chronobiologist at Ludwig-Maximilians University in Munich, Germany, says his research shows human circadian body clocks—set by light and darkness—aren't able to adjust to clock-moving that shifts daylight from morning to evening. He says extra light in the evening only puts people further behind, increasing exhaustion and susceptibility to illness.
One thing on which many proponents and opponents of DST agree is that the current scheme of moving the clocks twice each year creates an inconvenience and forces a rather unnatural adjustment—which is just what will happen again when daylight saving time ends on Sunday, November 6, across most of the United States.