Diagnosability is a basic property of Discrete Event Systems that relates to the observability of concealed events. Basically, it means that every failure (a distinct instance of unobservable event) can be eventually detected after a finite number of observations. In this work, we are interested by the diagnosability of systems modelled using labelled Time Petri nets (TPN), an extension of Petri nets in which we can associate timing constraints to transitions. This means that we take into account the date at which events are observed and that we want to detect failures in a bounded time. We are also interested by the detection of patterns of events (sequence of observable events that are part of some given regular language) instead of the occurrence of a single fault.