For those who are willing to install stuff outside Synaptic there’s Alarm clock (haven’t tried it myself), but for the rest of us it looks like there’s no going round Evolution.
Thanks to Mr. Murphy, I went looking for a reminder app right after uninstalling Evolution, for which I had no use. Of course, this caused the calendar available from the panel’s clock not to have any such functionality at all, so I had to go back and re-install Evolution. It’s a shame, because although Evolution’s calendar probably does everything you could ever want, it seems like overkill for someone used to the rather minimal Freebie Notes from Power Soft in Windows.