People often underestimate their completion times of future tasks or events. The phenomenon of optimistic time prediction is called the planning fallacy. Prior research has demonstrated that individuals are less likely to make optimistic predictions about events that are temporally relatively close. Furthermore, events involving relatively more effort are perceived as temporally closer. Hence, we recruited 102 undergraduates and conducted an experiment to test whether a high-effort assignment would reduce perceived temporal distance to the deadline and, thereby, reduce the planning fallacy. The results showed that participants in the high-effort condition perceived the deadline as temporally closer, generated less optimistic time predictions and were less likely to commit the planning fallacy. The inverse relationship between the amount of required effort and the likelihood of committing the planning fallacy was mediated by perceived temporal distance to the deadline. Our findings provide an innovative approach for reducing the planning fallacy in students.