Taskwarrior

Calcurse is a text-based calendar and scheduling application. It helps
keeping track of events, appointments and everyday tasks.
A configurable notification system reminds user of upcoming deadlines, and the
curses based interface can be customized to suit user needs. All of
the commands are documented within an online help system.

apt-get install calcurse

(reads icalendar, has some good curses work, fairly limited and annoying)