I even encounter madness with just one calendar
I am a happy Linux greybeard at my place of work, so I only occasionally start-up my Windows device.
Once I am logged in, Outlook reminds me of meetings that have already occured days ago.
I guess, there was a fruitless discussion on a potential cut-off period: "How long should we remind users of passed meetings?"
Well, I guess they settled on the Salomonic-moronic approach, "Let's remind the users of all past meetings"
This is equally good (we're reminding them) and bad (we're reminding all of them).