This paper proposes a new approach for automatically dating a photograph, based solely on its content. Building on recent advances in computer vision, the images are first described by a set of features. Then, the age group of every image is predicted by a classifier trained with annotated data. The key strength of our approach -- which makes it perform better than existing ones -- is the introduction of an ordinal classification framework, particularly adapted to the type of data to be predicted (age groups). The approach is validated on a recent challenging dataset for which it produces state-of-the-art results.