Datebook is a calendar program that keeps track of appointments for specific
times and dates as well as recurring (daily, weekly, monthly, yearly) events.
Calendar entries may be at a specific time or have no time associated with them.
Datebook will also keep track of general 'to do' lists, phone numbers, etc.

Remind is an accompanying program that runs in the background and will display
a message 10 minutes before, 5 minutes before and at the time of the calendar
entry.