I did a quick scan of the events_trigger()'s and below is the list.
Doesn't look like there is a specific one for updating the calendar.
But you may want to hook into the event that results in the calendar being updated, for example the create/update of a course or the enrollment there in.
Anne.
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events_trigger($event, $eventdata);
events_trigger($eventname, $eventdata);
events_trigger('activity_completion_changed', $data);
events_trigger('assessable_content_uploaded', $eventdata);
events_trigger('assessable_content_uploaded', $eventdata);
events_trigger('assessable_content_uploaded', $eventdata);
events_trigger('assessable_content_uploaded', $eventdata);
events_trigger('assessable_file_uploaded', $eventdata);
events_trigger('assessable_file_uploaded', $eventdata);
events_trigger('assessable_file_uploaded', $eventdata);
events_trigger('assessable_files_done', $eventdata);
events_trigger('assessable_submitted', $eventdata);
events_trigger('assessable_submitted', $eventdata);
events_trigger('assessable_submitted', $eventdata);
events_trigger('blog_entry_added', $this);
events_trigger('blog_entry_deleted', $this);
events_trigger('blog_entry_edited', $entry);
events_trigger('cohort_added', $cohort);
events_trigger('cohort_deleted', $cohort);
events_trigger('cohort_member_added', (object)array('cohortid'=>$cohortid, 'userid'=>$userid));
events_trigger('cohort_member_removed', (object)array('cohortid'=>$cohortid, 'userid'=>$userid));
events_trigger('cohort_updated', $cohort);
events_trigger('course_category_deleted', $this);
events_trigger('course_category_deleted', $this);
events_trigger('course_completed', $this->get_record_data());
events_trigger('course_content_removed', $course);
events_trigger('course_created', $course);
events_trigger('course_deleted', $course);
events_trigger('course_restored', (object) array(
events_trigger('course_updated', $course);
events_trigger('groups_group_created', $group);
events_trigger('groups_group_deleted', $group);
events_trigger('groups_group_updated', $group);
events_trigger('groups_grouping_created', $data);
events_trigger('groups_grouping_deleted', $grouping);
events_trigger('groups_grouping_updated', $data);
events_trigger('groups_groupings_deleted', $courseid);
events_trigger('groups_groupings_groups_removed', $courseid);
events_trigger('groups_groups_deleted', $courseid);
events_trigger('groups_member_added', $eventdata);
events_trigger('groups_member_removed', $eventdata);
events_trigger('groups_members_removed', $eventdata);
events_trigger('lti_unknown_service_api_call', $data);
events_trigger('mod_created', $eventdata);
events_trigger('mod_deleted', $eventdata);
events_trigger('portfolio_send', $this->id);
events_trigger('quiz_attempt_started', $eventdata);
events_trigger('role_assigned', $ra);
events_trigger('role_unassigned', $ra);
events_trigger('role_unassigned', $ra);
events_trigger('test_cron', 'ok')
events_trigger('test_cron', 'ok');
events_trigger('test_cron', 'ok');
events_trigger('test_instant', 'fail')
events_trigger('test_instant', 'ok')
events_trigger('test_instant', 'ok')
events_trigger('test_instant', 'ok')
events_trigger('test_instant', 'ok')
events_trigger('test_instant', 'ok')
events_trigger('user_created', $DB->get_record('user', array('id'=>$user->id)));
events_trigger('user_created', $euser);
events_trigger('user_created', $newuser);
events_trigger('user_created', $user);
events_trigger('user_created', $user);
events_trigger('user_created', $user);
events_trigger('user_created', $usernew);
events_trigger('user_deleted', $user);
events_trigger('user_enrol_modified', $enrolment);
events_trigger('user_enrol_modified', $ue);
events_trigger('user_enrol_modified', $ue);
events_trigger('user_enrolled', $ue);
events_trigger('user_logout', $params);
events_trigger('user_unenrolled', $ue);
events_trigger('user_unenrolled', $ue);
events_trigger('user_updated', $DB->get_record('user', array('id'=>$oldinfo->id)));
events_trigger('user_updated', $euser);
events_trigger('user_updated', $euser);
events_trigger('user_updated', $euser);
events_trigger('user_updated', $euser);
events_trigger('user_updated', $existinguser);
events_trigger('user_updated', $updateduser);
events_trigger('user_updated', $user);
events_trigger('user_updated', $user);
events_trigger('user_updated', $user);
events_trigger('user_updated', $usernew);
events_trigger('user_updated', $usernew);
events_trigger('workshop_viewed', (object)array(..))