1. A method for dating photographic prints comprising: a) scanning a front side of a photographic print forming an image scan; b) scanning a back side of the photographic print forming a back scan; c) defining a database of photographic print watermarks, each photographic print watermark comprising a representation of a watermark pattern and an associated date range; d) analyzing the back scan using a cross-correlation process between the back scan and the watermark patterns in the database of photographic print watermarks to identify a matching photographic print watermark, and by further analyzing the back scan to determine a color of the photographic print watermark in; e) determining a date range for the image scan responsive to the identified matching photographic print watermark and the determined color of the photographic print watermark; and f) associating the determined date range with the image scan; wherein a matching photographic print watermark is identified when a signal generated by the cross-correlation process exceeds a predetermined watermark-dependent threshold value associated with each photographic print watermark, wherein a training process is used to determine the watermark-dependent threshold value for each photographic print watermark.