Unlike the presentation, interaction with data deals with all of the dialogs, customizations and preferences and their influence on the interface. While we usually see the month or week views of our calendars, the real magic always happens in the dialogs. Being able to quickly find the right time slot, creating an event, setting all of its parameters (such as attendees or location) and, finally, getting reminders that are perfect for you — all of these are what make a calendar useful.