Two experiments investigated young children's understanding of how and when knowledge was acquired. In Experiment 1, thirty 4- and 5-year-olds were shown or told about various toys hidden in distinctive containers in two sessions a week apart. In the second session, children were asked how and when they learned the containers' contents. They more accurately reported how, than when, the information was learned. In Experiment 2, thirty 4- and 5-year-olds were administered similar learning tasks but were additionally asked which information had been known longer. This comparative question elicited more correct responses, comparable to those regarding how learning occurred. Results from these direct comparisons of reports of how and when knowledge was acquired offer resolution to apparent discrepancies in prior empirical reports and contribute to a cogent characterization of children's developing understanding of knowledge acquisition. (Contains 2 figures and 2 tables.)