Recent interest in spatiotemporal data modeling has been primarily on data structures and access mechanisms, content-based description and query, or extensions of existing data models to satisfy the requirements of a specific representation of space and time. However, there is a need for a general conceptual data modeling language suitable for specification and analysis of applications based on different spatiotemporal representations. In this paper, an extension of a standard object-oriented modeling language--Unified Modeling Language (UML)--is proposed which includes support of object- and field-based representations of space, event-based and periodic representations of time, and alternative interpolation semantics. A new concept of attribute groups is introduced to allow concise specification of common spatiotemporal properties and constraints.