In the days that follow the twice-yearly “springing forward” or “falling back” of our clocks, you can count on lively coffee-break complaints about body clock confusion, taping the wrong show, or missed appointments.
For the last 20 years or so, daylight savings time started on the first Sunday in April and ended on the last Sunday in October. Starting this year, however, daylight savings time for most of the U.S. will begin on the second Sunday in March and end on the first Sunday in November. So we’ll get darker mornings and lighter evenings sooner than usual.
The change is all part of President Bush’s Energy Policy Act, mandated in 2005 as an attempt to combat growing energy problems. According to the California Energy Commission, household energy consumption is linked to how many hours there are between sunset and bedtime. When we go to bed we turn off lights and appliances that account for about 25 percent of home energy consumption. It is hoped the change will save 100,000 barrels of oil a day during the extension period, but some doubt remains over this figure.
The Effect on Our Mood
How will a longer stretch of dark mornings and light evenings affect us?
For one thing, we are all likely to become more active in the evenings.
Feeling that the best part of the day’s not over when we leave work can’t help but make us feel more optimistic, and outdoor exercise suddenly will be a nicer prospect! Social activities also are likely to increase when we’re able to savor more daylight. An hour of light after work means more opportunity for ball games, trips to amusement parks and shopping.
Other benefits may include a drop in crime, as people are not out so much in the dark, and an estimated drop in road traffic injuries, as people are leaving work and school in daylight. However, traffic accidents may rise initially: Following the spring shift to daylight savings time, when one hour of sleep is lost, studies have found a measurable increase in the number of fatal accidents. Lost productivity is another short-term drawback, as sleep-disrupted workers adjust to the schedule change.
Finnish researchers have found that the transition to daylight savings time reduces both our sleep duration and efficiency. They monitored the rest-activity cycles of ten adults for ten days a year over two years. After the transition they noted that sleep time was shortened by 60 minutes and sleep efficiency was reduced by 10 percent on average.
But on a positive note, depression rates are set to fall. Researchers from Quebec, Canada say sleeping late increases REM sleep, and excessive REM sleep is linked to depression. They reviewed two studies on depression and sunrise time in cities, and found it was “significantly correlated” with depression rates — later sunrise (corresponding to earlier rising times) was associated with less depression.
A study in the Journal of Periodontology suggests that a chance to enjoy extra daylight can extend the life and health of our teeth and bones. That’s because our bodies get vitamin D through sun exposure. Vitamin D, along with calcium, is essential for preventing bone and teeth disorders.
While polls indicate most people favor extending daylight savings time, there are opponents. The airline industry has said it will cost millions of dollars to change schedules, and numerous time-sensitive computer systems may be affected. Many businesses have been thrown into panic, but candy manufacturers have a reason to smile. This year, Halloween occurs during daylight savings time, giving trick-or-treaters an extra hour of daylight to make their rounds.
To stay in sync with the U.S., Canada and many Caribbean countries will extend their daylight savings time calendars. Daylight savings time is not observed in Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands, and Arizona.
Hildebolt C. F. Effect of Vitamin D and Calcium on Periodontitis. The Journal of Periodontology, Vol. 76, September 2005, pp. 1576-87.
Olders H. Average sunrise time predicts depression prevalence. The Journal of Psychosomatic Research, Vol. 55, August 2003, pp. 99-105.
Lahti T. A. et al. Transition to daylight saving time reduces sleep duration plus sleep efficiency of the deprived sleep. Neuroscience Letters, Vol. 406, October 2006, pp. 174-77.