1. A computer program product comprising a non-transitory computer readable storage medium having program code embodied therewith, the program code being executable by a processor to: generate a key that is associated with a first entity that is associated with a spacetime region, wherein the spacetime region represents a spatial region, a time interval, and a non-spatial feature, and wherein the first entity is associated with the spacetime region based on spacetime coordinates for the first entity; generate an anonymized key to be associated with the first entity from the key, the anonymized key and the key representing the spacetime region with which the first entity is associated; and compare the anonymized key with a previously anonymized key that is associated with a second entity to discover spacetime co-occurrence of the first entity and the second entity in the spacetime region.