This thread makes me feel like I've been dropped into an alien world. After several years of iPhones and after years of owning computers since we powered them with coal, I have yet to use a digital calendar. The only time I ever open the calendar app is to see what day of the week a certain day falls on. The only time I opened iCal on my Macs was when the skeuomorphism debate happened around the time of Forstall's exile. ("oh yeah, a leather bound graphical calendar really does look stupid...")
If every calendar app in the world stopped working immediately, my life wouldn't change.
I remember watching Steve announce iCal, and all the publish/subscribe stuff that it did, and I thought it would be ok for workgroups, but I couldn't see any reason for me to start filling it in for personal use. I mean, looking at some of the screen shots from the calendars mentioned (Sunrise, Fantastical, etc), I started cracking up while reading them. "Running in the park", "work from home", "get a haircut", and my favorite "mow the lawn". Really? Someone needs a notification from their calendar program to mow their lawn? Doesn't looking out the window help them?
Like I said, for workgroups, probably an interesting tool. For personal use, not any better than a piece of paper for me. What benefit do you guys get from using a calendar program? Lets hear some stories.