On November 7, clocks moved back an hour and once again Americans are discussing the pros and cons of daylight saving time. Opinions vary about the practice of setting standard time forward by one hour in the spring and restoring it by setting it back by one hour in the fall. For David Prerau, researching and discussing daylight saving time is a passion that has been part of a well-respected career in science.

Widely considered a leading international expert on the subject, Prerau, who studied physics at Brooklyn College in 1959 and 1960 and holds a Ph.D. from the Massachusetts Institute of Technology, became interested in daylight saving time while conducting technical research for the U.S. Department of Transportation. He noticed that discourse around the practice was largely confined to scientific and research communities and that even then, not much hard data was available. So he began extensive research and analysis of the history, practice, and effects of this twice-yearly event.

In his book Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time (Basic Books, 2009), Prerau details Benjamin Franklin’s original concept of awakening closer to sunrise as a way to maximize the benefits of daylight and minimize the cost of using candles at night. The objective of using as much daylight as possible is still thought to provide a universal benefit. However, the history of the practice has been marked by debate around the question: Should we keep or change the current system?

“Daylight saving time has had an impact on a wide variety of often unexpected areas, from energy conservation, agriculture, and transportation to recreation, street crime, television schedules, voter turnout, gardening, schoolchildren, vehicular accidents, the workings of the stock exchange, and even the inheritance rights of twins,” says Prerau.

He notes that to save electricity during a historic energy crisis in 1974, the United States tried changing the time system temporarily by extending daylight saving time to be year-round for two years. However, the results were very unpopular nationwide: The public complained about waking and going to work during dark winter morning hours when it is often the coldest, and they were also very concerned about the lack of safety for children going to school in the pitch black. In addition, sleep and circadian rhythm experts stated that exposure to daylight after waking is critical to good health. Due to the unpopularity of year-round daylight saving time, the country went back to turning its clocks forward in the spring after only one year, and cancelled the second year of the experiment.

Prerau supports keeping our time system as it is. He says that most people like and benefit from an extra hour of daylight in the evening during the spring, summer, and fall. So for most of the year, daylight saving time works. However, people strongly dislike waking in the dark in the winter, so they need the earlier sunrises of standard time. “The current time system is an excellent compromise; it allows us the benefits of daylight saving for most of the year, but avoids the problems of waking up and traveling in the dark to work or school during the coldest, darkest months of the year.”