As a freelancer I really hate "calendar invites". Every client, potential or associate uses a different tool and my email client cannot always "accept", often cannot insert into my own calendar and a lot of the time doesn't even show the "details". I simply can't have 4 or more calendar flavours on the go. Time zone differences don't always compute either. How about just a plain email that states the time and the time zone along with anything else I need to know?