Space, time, objects, and events are fundamental concepts in ontologies. For substantivalists that believe entities are located at regions (space or spacetime), a key issue to address is the relationship between entities and their located regions. There is rich literature on the ontologies of location and mereology of material objects, as well as their philosophical foundations, but relatively little on events and their location. Most existing event ontologies provide little beyond the signatures and simply associate an event entity to space and time. In this study, we propose a new location ontology for events that formalize the relationship between events and spacetime, where events and spacetime maintain their own mereologies. We also make ontological commitments to support the mereological harmony of events and spacetime and provide the rationale and axiomatization of these commitments.