Effective people know that time is the limiting factor. The output limits of any process are set by the scarcest resource. Time is also a unique resource. One cannot rent, hire, buy, or otherwise obtain more time. The supply of time is totally inelastic. No matter how high the demand, the supply will not increase. Time is totally irreplaceable. Within limits we can substitute one resource for another, copper for aluminum, for instance. They can substitute capital for human labor. We can use more knowledge or more brawn. But there is no substitute for time. Similar time-wasters abound in the life of every knowledge worker. Time is the scarcest resource, and unless it is managed, nothing else can be managed. The analysis of one’s time, moreover, is the one easily accessible and yet systematic way to analyze one’s work and to think through what really matters in it.