A CPU generates time stamp data using a timed result for the present time timed by timer and a set expression pattern. Then, the CPU generates modified time stamp data for a predetermined time period based on the time stamp data. The CPU identifies the maximum time stamp data through the printing range of the above time stamp data. The CPU reduces the font size until the maximum time stamp data becomes printable onto the printing medium. The CPU then sets the reduced font size as the font size for each time stamp data, etc., and carries out printing.