PURPOSE: To allow this date management system due to correspond to date change due to a national holiday or the like by correcting and registering only a national holiday arrangement table file corresponding to the holiday by preparing the national holiday management table file for storing information indicating the dates of national holidays independently of a date management common program.

CONSTITUTION: A computer system capable of being conscious of national holidays/sundays/weekdays is provided with a national holiday management table file 1 for storing information indicating the dates of national holidays. A date management common program 2 for managing dates in common in the computer system acquires the information indicating the dates of national holidays by accessing the file 1. An application program in the computer system acquires information relating to dates by accessing the program 2. A table maintenance/ management program 4 executes the correction/registration of the file 1 at an optional point of time.