An appointment book is a helpful tool for keeping track of important dates and scheduled meetings. However, there are various synonyms available to use instead of appointment book. Scheduler, planner, day planner, agenda, diary, and calendar are a few options. A scheduler is a simple tool used to manage schedules while a planner is a more comprehensive tool that includes goal-setting and weekly to-dos. A day planner is like a mini-scheduler that helps to manage your daily schedule while an agenda is a more formal tool used for taking notes and managing meetings. A diary is a personal record of your daily life while a calendar is a way to keep track of dates and upcoming events.