khal
Khal is a standards based CLI (console) calendar program, able to synchronize with CalDAV servers through vdirsyncer.
Features
(or rather: limitations)
khal can read and write events/icalendars to vdir, so vdirsyncer can be used to synchronize calendars with a variety of other programs, for example CalDAV servers.
fast and easy way to add new events
ikhal (interactive khal) lets you browse and edit calendars and events
only rudimentary support for creating and editing recursion rules
you cannot edit the timezones of events
works with python 3.8+
khal should run on all major operating systems [1]