Regular models are models for non-normal modal logics. By defining some model operations, including disjoint union, C2t_- bisimulation, generated submodel, and C2t_-ultrafilter extension, this study proves that a class of regular models can be defined in the temporal language if and only if it is closed under disjoint unions, surjective C2t_-bisimulations and C2t_-ultrafilter extensions, while its complement is closed under ultrafilter extensions. This characterization theorem explains the expressive power of temporal language over regular models.