Annoying Windows 10

The Windows 10 calendar reminder window has become very annoying.  At some point it downloaded the birthdays of everybody I knew on Facebook.  Now Facebook has apparently disconnected Windows/Microsoft from Facebook, so that the birthdays are now stored in some mystery calendar file.  But Windows 10 desktop keeps reminding me of them, every five minutes, and telling the reminder to dismiss does not help.  It just comes back over and over and over again.  And you can't delete the calendar entry, because it's not in a normal calendar.  The engineers at Microsoft are surprisingly stupid, despite doing a much better job in general on Windows 10 than on any previous version.