When a schedule is updated, a check is performed to determine whether matters concerning the updated schedule are included in a To Do List, in which all processes to be performed are registered, and a schedule list. When there is an associated undertaking, added to a task table is a notification task for notifying a user and reminding him of the existence of that undertaking. Then, a notification process for reminding the user of the schedule for the pending undertaking is performed under appropriate conditions.