We introduce temporal tagging, a general tagging principle that takes into account when tags were generated. We use this temporal information to identify points of interest in extended recordings of complex events. We empirically demonstrate the utility of the approach in a successful user trial of a system ChattyWeb (CW) that allows students to access lecture recordings. CW coindexes students' digital handwritten annotations and lecture recordings. In our trial, students were able to use CW to successfully answer questions related to recorded lectures, and to use others' digital notes to facilitate this. We describe how tags are generated at low cost, as a side-effect of current user practice, addressing a common limitation of tagging approaches.