A user had a calendar appointment on Tuesday from 10am to 11 am. She had 2 other people on the invite. She changed it yesterday to be Thursday at 10-11. The two people accepted the changes and their calendar looks good. The user who made the appointment still has it on Tuesday at 10-11am.
One really odd thing is that the reoccurrence symbol (the two arrows in a circle) has a line through it to show that she broke the main reoccurring time. So while the calendar has the wrong date but correct time, it also shows that she modified that one instance.