For "Group Time Table" application which has 2 users: general user and secretary user
General user use "To do list" application for record a activity to do something. He can record only his activities, date, time, place, alert time, alert message etc. (You can add more data for this application.)
Secretary user uses "To do list" application for time table management the free time. He can book the free time for an appoint of member group.