Evolution makes a distinction between meetings (involves invites to one or more other people) and appointments (involve reminders/calendaring for just yourself).

However, often an existing appointment will become a meeting. For example:
* You add an appointment for yourself to the calendar to remind yourself of an upcoming event.
* A few days later, one or more people expresses an interest in the event too.
* You want to change your appointment into a meeting, and invite those people.
* Evolution does not seem to provide a way to do convert your appointment into a meeting.

It would be very helpful if there was a way to add attendees to appointments (i.e. make appointments into meetings), and conversely remove all attendees from meetings (i.e. make meetings into appointments). I.e. the distinction between appointments and meetings is quite arbitrary - there are just events - some of which you want to tell other people about, and some of which you don't, and things can and do change between those two states. What matters most to the user is the event, not whether you are telling other people about it, but the evolution workflow seems to make deciding whether other people are going to be invited or not the very first decision you have to make, which is simply not the user's primary concern.