As the living Web expands, worldwide volumes of Web archives constantly increase, making difficult to identify relevant archived contents. Here we propose an application for detecting historical events out of a corpus of Web archives and based on an entity called Web Fragment: a semantic and syntactic subset of a given Web page. The Web fragment has the particularity to be indexed by its edition date instead of its archiving date. We apply our framework on an archived Moroccan forum and witness how it reacted to the Arab Spring at the end of 2010.