The high availability and scalability of weakly-consistent system attracts system designers. Yet, writing correct application code for this type of systems is difficult; even how to specify the intended behavior of such systems is still an open question. There has not been established any standard method to specify the intended dynamic behavior of a weakly consistent system.In this paper, we present a event-based parallel temporal logic (EPTL), that is tailored to specify properties of weakly consistent systems. In contrast to LTL and CTL, EPTL takes into account that operations of weakly consistent systems are in many cases not serializable and have to be treated respectively to capture their behavior. We embed our temporal logic in Isabelle/HOL and can thereby leverage strong semi-automatic proving capabilities.