A calibration process that manages calibration execution timings for a plurality of printers uniformly to keep the print characteristics of individual printers constant. More, specifically, in the printer, the calibration record information representing the time that has elapsed from the previous calibration is obtained. Based on this record information, a check is made to see whether the elapsed time has exceeded a predetermined period. When it is decided that the predetermined period of time is exceeded, a warning is displayed to urge the user to execute the calibration. With this process, the user can easily perform the calibration at predetermined intervals.