My mind was blown when I discovered this little gem recently:<p><a href="http://www.computerhope.com/unix/ucalande.htm" rel="nofollow">http://www.computerhope.com/unix/ucalande.htm</a><p>Place a text file at ~/.calendar/calendar with one event per row, containing the date and the title separated by a tab. Type calendar and you'll get a list of what's coming up in the next few days. You're done.<p>Being a venerable UNIX utility there are of course a variety of options (switch to view X days in the future, support for including external calendars, support for recurrence, etc.). Weirdly, it lacks any concept of start and end time, but this is easy enough to simply include in your appointment's title. And no free/busy or special sharing mechanism (though you could certainly compose your calendar of several files and expose them on a web server easily enough).<p>It's not about to replace a full-blown calendar app for power users, but if you're the type of person who has a fairly light meeting schedule and spends a lot of time in a terminal... I was immediately done with all other calendar software and consequently all the problems of said software when I stumbled across this thing.