A general approach for temporal reasoning, the event calculus, has been modified and applied to the development of a historical deductive object base. The event calculus is a theory of time in first-order logic augmented with negation as failure. It is shown how an object-based variant of the event calculus may be used for representing changes to the states of objects. We first present the formulation and describe the maintenance of a historical object-oriented database by the use of events. The resulting formalization can be executed as a logic program. We then discuss the implementation of a practical database system based on the theory we develop. The additional detail needed to develop a system of realistic scale is outlined. The aim is to present the object-based event calculus as a unifying framework for the implementation of a deductive and object-oriented database system.