Even simple hybrid systems like the classic bouncing ball can exhibit Zeno behaviors. The existence of this type ofbehavior has so far forced simulators to either ignore some events or risk looping indefinitely. This in turn forces modelers to either insert ad hoc restrictions to circumvent Zeno behavior or to abandon hybrid modeling. To address this problem, we take a fresh look at event detection and localization. A key insight that emerges from this investigation is that an enclosure for a given time interval can be valid independently of the occurrence of agiven event. Such an event can then even occur an unbounded number of times, thus making it possible to handle certain types of Zeno behavior. © 2013 IEEE.