Managing and scheduling events and meetings using the calendar in Microsoft Teams Free
I think it is an issue only for the "week" view, not "day" nor "work week" views. Also, the "week" view isn't showing the whole week, just the work week (for those who happen to be monday thru friday workers. I liked the theory that it is related to leap year, but the calendar "week" view is still one day off when displaying a week in January (before leap day), so I think it might be something else.