1. A computer-implemented method for producing a calendar, comprising: recording a report that includes an image and is contributed by a contributor; distributing the report; counting the number of viewings of the image in the report by a viewer; acquiring information on a photographing density, where the photographing density expresses the number of images photographed or contributed in a predetermined period before and after a time and date when the image in the report was photographed or contributed; extracting the image for a calendar on the basis of the number of viewings and the photographing density from among the images contributed or photographed in a predetermined month; receiving a calendar production instruction; and producing a calendar for the predetermined month when the image was contributed or photographed, using the image for the calendar according to the calendar production instruction.