Google Calendar

Google Calendar is a very complex application that can perform many tasks, not just help us remember the birthdays of everyone we know. In fact, you can use it to plan meetings, for reminders regarding a particular event, and primarily to use it as a complete schedule.
 
Users can change how they view their calendar, and they can modify the way the date is displayed and used, based on their location, the application can import events straight from Gmail, such as flight, hotel, concert, restaurant reservations, and so on, or just to add goals that need to be met.
 
Furthermore, Google Calendar is also able to import data from all the installed calendars, including Exchange.