Re: Amen to all that
iCalendar exists. If some shitty proprietary software companies are too lazy to make their programs work with it (or are being deliberately obstructive about it), that's their problem.
Semi-ironically, it was probably Apple (who are very good at having the wisdom to learn and borrow from open source and open standards, but not always the best at giving back) who have probably done the most to push the adoption of the iCalendar data format.