Money can buy you happiness, a new study shows. But it must be spent wisely: not on material possessions, but on time-saving activities that will contribute to living a more satisfied, relaxed life.

A team of researchers led by Harvard Business School professor Ashley Whillans surveyed nearly 4,500 people, including millionaires, from the U.S., Canada, Denmark and the Netherlands on their spending habits and life satisfaction with the goal of tackling what they call the “time famine of modern life.”