a schedule management system includes a schedule data table which stores the schedule data including an identifier of a schedule owner , the time zone , activity and the state of the schedule . a definition data table stores the definition data for determining the relation between the registration and display of the schedule and the schedule and the state in he schedule data . a schedule data registration unit accepts a schedule reservation request , determines whether the schedule registration is permitted or not based on the schedule state of the schedule data existing in the schedule data table and the definition data , and when the schedule registration is permitted , registers the reservation schedule in the schedule data table . a schedule data approval unit accepts a request from the schedule owner for approving / disapproving the schedule and rewrites the schedule state of the corresponding schedule data in the schedule data table . a schedule display unit accepts a schedule display request , determines whether the existing schedule is displayed or not based on the schedule state of the schedule data existing in the schedule data table and the definition data , and displays only the schedule data determined for display .