Calcurse is a calendar and scheduling application for the command line.
It helps keep track of events, appointments and everyday tasks. A
configurable notification system reminds user of upcoming deadlines, the
curses based interface can be customized to suit user needs and a very
powerful set of command line options can be used to filter and format
appointments, making it suitable for use in scripts.

There is an optional dependency on httplib2 if you want to use the
calcurse-caldav utility.