In the past few years, due to the development of the mobile devices and the improvement of database technology, the geometric information has become widely available. Identifying object groups based on spatial-temporal dimension is an emerging research topic. Previous work has incorporating the spatial and temporal information pertaining to moving objects in finding mobile groups. Considering that mobile groups tend to exhibit some calendar-like temporal features, we define a new temporal presentation mechanism called flexible calendar pattern, which allows users to specify the desired calendar patterns at a coarse level. In addition, we developed efficient algorithms for mining mobile groups pertaining some user-specified flexible calendar pattern. The proposed algorithms are evaluated via the synthetic data generated by IBM City Simulator. The results show that our approaches prove to perform more efficiently than other intuitive approaches.