This study investigated the development of the ability to reflect on one's personal past and future. A total of 64 4- to 6-year-olds received tasks of delayed self-recognition, source memory, delay of gratification, and a newly developed task of future-oriented action timing. Although children's performance on delayed self-recognition, source memory, and action timing improved with age, their performance on delay of gratification did not. Children's errors in source memory and action timing were solely and strongly associated with each other in older children (5-6 years) even after controlling for age and verbal ability. Results are discussed in terms of mental time travel underlying episodic memory and future thinking that includes both the projection of oneself into the past and future and the appreciation of events' temporal relations.