America has a time problem. About half of us tell pollsters that we don't have enough time to do what we want. Another survey found that most people would prefer two more weeks of vacation than two more weeks of pay. And every new "labor-saving" technology -- e-mail, smart phones -- seems to make things worse, not better.

Books for the time-starved and productivity-challenged would fill a small library. Beyond the books, there are the seminars, videos, apps and "methods" (like "Getting Things Done") that feature books, videos, and seminars.

Yet for all the advice that has been offered, I doubt anyone has come up with the bit of wisdom on offer from a professor at Harvard Business School: Spend more time doing things for other people.

This is, of course, completely absurd. How could taking on another task possibly help?

The answer has to do with the important distinction between time -- that thing that can be measured with atomic clocks, that marches on, merciless -- and subjective time, our experience of the flow of events. And this is why the advice, the product of recent scientific study, is both unexpected and wise.

"It is not so much how much time you have," says Harvard Business School's Michael Norton, "as how you feel about what you can get done in the time that you do have."

Norton, working with Cassie Mogilner at the University of Pennsylvania and Zoe Chance at Yale, arrived at this conclusion through a series of investigations into our perception of time. Students were asked to either give time away (writing an encouraging note to a gravely ill child) or waste time (counting instances of the letter "e" in a Latin text). Afterwards, the letter writers felt that they had more time, according to a survey.

But maybe, the researchers reasoned, doing the time-wasting task was simply unpleasant, and this bad mood made people feel they had less time. So they did another experiment, asking students on a Saturday morning to do something they hadn't planned to, either for themselves or for someone else. They found that the people who did a good turn for another felt like they had more time.

Finally, they did an experiment that got right to the heart of the matter. They told a class that, at the end of a lab session they would be helping at-risk students from a local high school by editing an essay they were working on. When the time came, half were given the essays to work on, and the other half of the class was told that there were no more essays to work on, and they could leave early.

Here, then, the researchers were comparing the effect of doing something for someone else, and having a sudden, unexpected windfall of time. As they report in the journal Psychological Science, the people who helped with the essays said that they felt they had more time to take care of their work than the people who'd been given free time.

Allow this strange fact to sink in: The best solution for not having enough time is not being given more time.

It turns out that people are extraordinarily bad at estimating how much time a task will take to complete; this is known in psychology as "the planning fallacy."

"One of the things that can happen when you are overbooked or overstressed is that even the tiniest thing that comes up can feel insurmountable," says Norton. "We have all had the experience of getting that one more e-mail and feeling like, 'Oh, I am doomed.'"

The planning fallacy means that we have a poor sense of how much effort it will take to complete that to-do list we carry around with us. And this, in turn, means that the stress we all feel -- how can I get it all done? -- is only loosely connected to reality.

Norton argues that doing something for someone else provides a tremendous boost in our confidence that we can get things done. It makes us feel in control of our lives -- effective. The future feels more open.

There is certainly an upper limit to this effect, a point at which the hours of helping others become an additional stress. And, clearly, improving one's time-management skills is bound to help.

Yet the research solves a central paradox: Americans feel daunting time pressures, and yet, by any historical measure, they have a tremendous amount of leisure time. We are all busy, yes. But we also labor under potent illusions, and isn't it a wondrous thing that we can help ourselves see through them by lending a hand to someone else?