Since first concepts and prototypes for integrated geographic information systems (GIS) have been designed, incorporation of time has always been a matter of research, philosophical debate, and development of innovative ideas. Commercially available information-system packages usually do not provide support for time integration in a satisfactory way, as their design follows a cartographic 2.5D-model approach. This shortcoming is particularly problematic when designing GIS data models for geologic (map) data, which are spatially 3D, and – by definition – temporal, as geology is all about connecting time and space to physical units. Despite its time-relevance, classical GIS-based geologic data models cannot implement time and temporal information, which is usually hard-wired into relations as attribute values. Consequently, and due to this structural problem, data integrity can be at risk, time queries are not possible, and the full potential of working with geologic map data cannot be unlocked. We herein discuss basic ontologic concepts of time in geology , and incorporate these aspects in order to provide ideas and potential solutions of approaching time in GIS-integrated data models. 1 Aims of Study GIS data models are paramount for efficiently maintaining integrity, administrating contents and querying/analyzing data, which are undergoing regular updates and changes in the course of projects. In geologic sciences, data models should allow the integration of (a) spatial data, i.e., geometries in connection with their geologic attributes, as well as their (b) temporal reference, i.e., timing of geologic events, for purposes such as analysis and map production. Our work is focused on establishing a generic time-integrated data model for geologic mapping and generation of map output. Parts of this work have led to discussions on the nature of time integration and to conceptualizations with respect to the treatment of time inherently related to geologic units, and, thus, geologic map products. GI_Forum ‒ Journal for Geographic Information Science, 1-2015.