A basic question in mining data from an intelligent tutoring system is, “What happened when ... ?” We identify requirements for a tool to help answer such questions by finding occurrences of specified phenomena and browsing them in human-understandable form. We describe an implemented tool and how it meets the requirements. The tool applies to MySQL databases whose representation of tutorial events includes student, computer, start time, and end time. It automatically computes and displays the temporal hierarchy implicit in this representation. We illustrate the use of this tool to mine data from Project LISTEN’s automated Reading Tutor.