Philosophers, psychologists, and economists have reached the consensus that one can use two different kinds of regulation to achieve self-control. Synchronic regulation uses willpower to resist current temptation. Diachronic regulation implements a plan to avoid future temptation. Yet this consensus may rest on contaminated intuitions. Specifically, agents typically use willpower (synchronic regulation) to achieve their plans to avoid temptation (diachronic regulation). So even if cases of diachronic regulation seem to involve self-control, this may be because they are contaminated by synchronic regulation. We therefore developed a novel multifactorial method to disentangle synchronic and diachronic regulation. Using this method, we find that ordinary usage assumes that only synchronic––not diachronic––regulation counts as self-control. We find this pattern across four experiments involving different kinds of temptation, as well as a paradigmatic case of diachronic regulation based on the classic story of Odysseus and the Sirens. Our final experiment finds that self-control in a diachronic case depends on whether the agent uses synchronic regulation at two moments: when she (1) initiates and (2) follows-through on a plan to resist temptation. Taken together, our results strongly suggest that synchronic regulation is the sole difference maker in the folk concept of self-control.