Briefly;  I'm investigating how to automatically create appointments in my
(and others') calendars.

I've been able to guess and map some fields to others - is there a reference
to describe how to format properly for all fields (reoccuring, label, etc?)

I see evite does this via a .vcs file - is there a reference as to what
items can be saved in the .vcs file?

An appointment has;
Subject, Location, Label, Start Time, End Time, (all day event checkbox),
Reminder, Show time as, Body, Contacts and Categories fields.

Q287625 indicates these fields;
DTSTART, DTEND, LOCATION, CATEGORIES, DESCRIPTION, SUMMARY and PRIORITY.