Geological time description largely rests on an event based chronology based on the stratigraphical model. It uses a hierarchy of chronologically ordered geochronological units and boundaries. In order to be easily dealt with within large databases used by complex engineering systems, the geological time chronology must be formalized. Stratigraphical time successions should accordingly be described by using adequate semantic tools (ontologies) complemented by a set of logical rules. At present, geological time formalization mainly rests on the GeoSciML model. This model is fit for describing individual geological time scales but does not provide all the necessary tools for comparing various time successions and for operating full stratigraphic correlations. For complementing the GeoSciML model, we define two ontologies for geological time description and for geological dating. They extend the GeoSciML model, so that it becomes possible to fully use the Allen rules for operating time correlations between any couple of time scales or stratigraphic successions. We additionally propose a codification resting on the defined ontologies, which allows operating all age identification and correlation by means of simple computation rules.