Some events are closely related to the definition of a period. We mark them as “starting event” or “terminating event”. A frequent intuition is that some kind of distinct event should be responsible for the upcoming of a new cultural phase (as required by Biers 1992). The question is: can a single historical, religious, military, political or physical event have a definitive affect on a period? Did, for example, an earthquake or a volcano eruption as the one that happened in Santorini determine the specific period? We regard that an event may be one of the catalytic factors to social change and thus be loosely synchronized with the end points of a period. Only the rare cases of complete extinction actually terminate a period in the absolute sense. Generally however, we do not regard those events as causal to the properties of a period, and the change of a period may quite well happen without such an event. Th erefore we use these events as chronological markers, “meetings” (Doerr, Plexousakis, Kopaka and Bekiari 2004) of items, objects and persons that were present in states/events, rather than as part of the definition. Such events are not regarded to be creating types of periods in the sense of cultural phenomena.