Professor J. Gregory Dees, “the Academic Father of Social Entrepreneurship,” passed away shortly before Christmas. He wrote the seminal definition of social entrepreneurship and launched Harvard’s social entrepreneurship program, Duke’s Center for the Advancement of Social Entrepreneurship, and Stanford’s Center for Social Innovation. Greg would have turned 64 this year. Had he followed a traditional career path, perhaps hoping to donate or volunteer after his retirement, it’s likely he would have accomplished far less.

We all understand the time value of money – an amount invested today, because of interest, is worth more than the same amount invested at a future date – but we are less familiar with the time value of service. Positive impacts also have a multiplier effect, accruing a type of social interest. For example, if we provide adequate nutrition to a growing child today, they will remain healthier, care for their future children better, and contribute more to society than if we wait years or decades to help.

The time value of service becomes even more striking when we consider premature mortality. Each year, 760,000 children around the world die from easily preventable and treatable diarrheal diseases. Waiting to help does them no good at all. Waiting doesn’t do us any good, either. The uncertainties inherent in all our lives may limit our ability to give time or money after retirement: service deferred is often service not rendered.

And that robs us of the personal renewal and enrichment that comes from helping others. Of course, there is an opportunity cost to such work, much like the choice between putting money away for retirement or spending it on a well-earned vacation. How can we do what we know is important, but still satisfy the obligations of our own wellbeing and that of our family? Fortunately, there is a spectrum of ways we can engage in service, from small charitable donations to devoting our careers to that pursuit, as Greg Dees did in his work expanding the field of social entrepreneurship.

We can involve our family in shared volunteering, starting a tradition of giving during the holidays, or convincing our friends to join us in pro bono consulting for a local nonprofit. Our time is valuable, though, and we may wish to choose those pursuits that render the greatest benefit (and joy) relative to our contributions.

There are many problems and many ways to address them, but some are larger than others, and some approaches will create a greater social return over time. If we hope to create a real impact, to ensure a positive legacy, to leave the world better than we found it, we must not wait. Greg recognized this, and in his characteristically understated and selfless way, set about creating impact and giving others wings to do the same.

Others far better known passed away this year, but few had the impact that Greg did. His parting gift to us is the knowledge that we, too, can all make a positive difference – but cannot know how much time we have been given to do so. Better to start now.