C-O Diagrams have been introduced as a means to have a more visual representation of normative texts and electronic contracts, where it is possible to represent the obligations, permissions and prohibitions of the different signatories, as well as what are the penalties in case of not fulfilment of their obligations and prohibitions. In such diagrams we are also able to represent absolute and relative timing constraints. In this paper we present a formal semantics for C-O Diagrams based on timed automata extended with an ordering of states and edges in order to represent different deontic modalities. As a proof of concept we apply our approach to two different case studies.