Our A4 size paper calendar - a month to view Red&Black with ample space for notes - allows the entire household to see at a glance who's got appointments coming up, who needs the shared car so that no accidental double-booking occurs.
I take it with me when I know I'll be offered future appointments, and have only been giggled at once, until I explained the household system. That, he said, sounds extremely easy.
It is. What's more I keep the previous year's calendar beneath it, so when I want to check when the boiler needs a service, or when an annual medical review is due, it is so much easier to simply flick back than go hunting in the relevant file.