I am beginning to regret using Thunderbird and Lightning rather than Outlook. At least Microsoft was intelligent enough (for once) to allow an appointment stored in an .ics file to be imported into my calendar. Lightning forces me to create a new calendar for a single appointment. That's just plain stupid. By the time I get back from a doctor/dentist appointment, there is already an email with an .ics file with the relevant information about my next appointment already sitting in my mailbox. I just can't do anything useful with it without going back to Outlook.

Searching the web for a way to do what I want all say go to File -> New -> Calendar. I don't want a new calendar for this. I don't need a separate calendar for every single event/appointment. Intuitively, they should all be able to be imported into the calendar of my choosing. In the days when physical calendars were the way this was done, did you (or your parents) buy a new calendar for every appointment, meeting, vacation day, etc you had? Why should it be any different for electronic calendars?