This paper introduces a world history ontology that supports reasoning of truth/falsehood of historical descriptions in natural languages. The core of the ontology includes an event classification according to certain basic properties such as necessary/sufficient conditions for the existence of events in the real world. We will discuss how this ontology functions in solving world history problems in Japan's National Center Test for University Admissions, especially in the reasoning of "falsehood" of sentences and bridging of the "granularity difference" between target sentences and knowledge resources.