org-icalendar-with-timestamps

org-icalendar-with-timestamps is a variable defined in `ox-icalendar.el'.
Its value is

active

Documentation:
Non-nil means make an event from plain time stamps.

It can be set to `active', `inactive', t or nil, in order to make
an event from, respectively, only active timestamps, only
inactive ones, all of them or none.

This variable has precedence over `org-export-with-timestamps'.
It can also be set with the #+OPTIONS line, e.g. "<:t".

You can customize this variable.