Farmer Jason Escobar tries to get Heidi into the barn at the Portsmouth dairy farm that’s been run by three generations of Escobars. Farmers have long opposed the time change.

Providence Journal / Bob Thayer

Fall back. But don’t spring forward anymore. You’ll be a season late.

This weekend ends daylight-saving time as we know it, which will now start earlier and last longer.

Next year, instead of beginning in spring, the first Sunday in April, daylight-saving time will start in winter, the second Sunday of March. And instead of concluding the last Sunday in October, it will be the first Sunday in November.

Politicians made this possible, not by adding daylight to the earth, but by shifting our exposure to it, from mornings to evenings, and making the change law.

How this law will affect our lives depends on who you ask: Michael Downing or David Prerau. Both men live outside Boston and last year both wrote books about daylight saving through the same publisher, Avalon. One man favors its expansion, the other doesn’t.

“There will be an outcry,” Downing says.

Downing, a creative writing lecturer at Tufts University, authored SpringForward: The Annual Madness of Daylight Saving Time.

“This expansion is probably a reasonable thing to do,” Prerau says.

Prerau, a consultant to Congress last year on daylight-saving time and co-author of three Department of Transportation reports on the subject, wrote Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time.

On daylight-saving time history, the two authors agree. One calls it madness, the other curious – with times of expansion, contraction and erratic implementation, until standardization in 1966.

If more of our waking hours are filled with sunshine, there’s less need for electric light. That’s the thinking. And the practice reportedly saves energy, which is why an expansion of daylight-saving time was included in the Energy Policy Act of 2005.

However, not everyone supports the reports of energy savings.

“The most optimistic studies tell us we ‘might’ save as much as 1 percent on domestic electricity,” Downing says. “It’s never been established.”

Prerau authored some of those studies from the 1970s. He says the findings were conclusive: a 1-percent reduction in energy usage and a 1-percent reduction in traffic accidents.

“When you’re a technical person as I am, you never say something is 100-percent true,” he says. “You say ‘the indications were.’ ”

Energy circumstances have changed, according to Downing. Oil now plays a much smaller part in producing electricity, he says, accounting for less than 5 percent of it.

“So the 100,000 barrels-of-oil-a-day savings is irrelevant,” Downing says. “The figure is impossible, not just implausible.”

“The findings had nothing to do with oil, but energy generated,” Prerau says.

Downing agrees some electricity is saved by daylight-saving time. If people’s waking hours are brighter, it stands to reason they may use less artificial light. But, he says, that’s only part of the energy issue.

“Gasoline consumption is never considered when we talk about energy saving,” Downing says. “If you give Americans an hour of sunlight in the evening, we know they will drive to a park and watch a baseball game or go to the mall.”

Prerau says people may be just as likely to sit outside and watch the sunset, and maybe have a barbecue.

It’s not just energy concerns that drive the daylight-saving time expansion, according to Downing and Prerau, it’s commerce. People don’t just drive to the mall; they shop there.

“A lot of people are asleep and businesses are closed when the sun rises,” Prerau says. “Many people are awake and businesses are open when the sun sets.”

“The important reason [expansion of daylight-saving time] passed is to increase consumer spending,” Downing says. “Congress is working on behalf of retailers.”

The biggest business to benefit from daylight-saving time, according to Downing, has a sweet tooth. At this time next year, there will be one more hour of daylight trick-or-treating.

“The reason a week of daylight-saving time is being added in the fall is the American candy makers have been pressing for it for 35 years,” Downing says.

People may long for a simpler, albeit contested, explanation for daylight-saving time: farmers. Don’t look at them, Downing says. They’ve long opposed the practice and have learned to live with it.

“People often mention that farmers work from sunrise to sunset,” says Louis Escobar of Escobar Highland Farm in Portsmouth. “You can quote me: ‘We have lights. We have lights on the tractors. We have lights in the barn.’ ”

Farmers, cows, everyone adjusts, with some consequence, according to Mary Carskadon, director of the Bradley Hospital Sleep Lab and professor of psychiatry and human behavior at Brown Medical School.

“Our biological timing mechanism is most sensitive to light at the beginning and end of the day,” she says “Light at the end of the day pushes our clocks later.”

But, according to Carskadon, our biological clocks are increasingly pushed or powered by something other than the sun.

“Sunrise and sunset are not our major light sources anymore,” she says.

Morning people around here may moan the darkened start of daylight-saving time. But the most affected people, according to Downing, are those on the western edge of time zones. In those places, he says, “people won’t see the sun until 8:30 or 9 in the morning the first week of November.”

The most serious charge made against daylight-saving time is that it endangers school children at darkened morning bus stops, but Downing finds the statistical evidence weak.

“Daylight saving accrues dubious credit for fossil-fuel savings and dubious blame for school bus accidents,” he writes.

The issue now is not daylight-saving time, but its expansion. More sunlight in March, according to Downing, may not get more people outside in New England, but a week in November could help golf courses.

Daylight-saving time also helps reduce crime, according to Prerau.

“One method we use to prevent crimes is to turn lights on, in parking lots, streets and in our homes,” he says. “It’s recognized by the law enforcement community to deter crime.”

Downing disagrees. “We know the highest crime rate in every part of the country is the summer, when there’s more sunlight than at any time of the year. When people talk about daylight-saving time, no one mentions that. Our brightest days are our most crime-ridden. Congress is giving us more of that.”

Statistics can’t tell the whole story of daylight-saving time, according to Prerau.

“From a quality-of-life standpoint, the extra hour in the evening is generally enjoyed by most people,” he says.

The biggest losers, according to Downing, will be small software makers that hadn’t programmed for a change in daylight-saving time.

If people don’t like the expansion of daylight-saving time, which Downing points out has become standard time since it’s now eight months of the year, we can always go back to a more traditional spring forward and fall back. Congress approved the expansion of daylight-saving time with a reversion clause, which may be enacted pending a report by the Department of Energy.