Dealing with service composition is an important and challenging issue of distributed systems. Existing works investigate mechanisms for analyzing and synthesizing a composition based on qualitative properties which characterize operations and/or messages choreography constraints. Apart from these qualitative properties, quantitative properties such as time related features are a crucial setting to consider. Augmenting service's behavior with timed properties increases the expressiveness and brings new difficult problems. This requires defining rigorous verification and composition primitives for taking into account such properties. In this chapter, we present a formal composition and verification approach which considers quantitative timed properties assigned to qualitative properties. The chapter starts with a general introduction. Then, it introduces the concepts related to timed Web services, timed conversations and protocols. The following section introduces the notion of composition of Web services with emphasis on the temporal dimension, and defines a formal composition approach. This approach relies on the generation of a mediator which aims surpassing timed conflicts. The next section presents validation primitives based on model checking techniques to verify and validate timed compositions. An implementation of the concepts previously introduced is then described. Before concluding with a larger consideration of time implication in Web services definition and composition, and with open issues, we present a study of the state of the art.