Component-based software engineering is widely used for developing large and complex software systems. In particular, real-time systems should benefit from this technique to handle complexity and deal with dependability. In real-time systems, applications should not only be logically correct but also behave within time windows. In this paper, we present a metamodel for component-based software description that integrates timing issues. Our metamodel is built by focusing on four functional aspects: interface, static behavior, dynamic behavior, and interaction protocol, to achieve a complete functional model of software components. For each aspect we define its associated time model. Such a time model can be used to check a component’s design against certain properties and to compute the timing properties of component assemblies.