For modelling and verifying agent systems, many researchers have proposed different logical systems. Since agentbased systems are designed to operate in dynamic environments such as the Internet, it is also important to model the temporal aspects of such systems in a systematic way. In this paper, we use a temporalised epistemic logic called TEL for formalising agent-based systems. We also propose a labelled tableau system and a model checking method for this logic. With logic TEL and its associated proof system, we are able to reason about, and verify agent systems operating in dynamic environments.