Managing and scheduling events and meetings using the calendar in Microsoft Teams Free
I think its a bug.
Works fine when you are on a 'day' or 'work week' view.
Which means the calendar view is doing either 1 or 5 days.
If you select 'Week' view which is more than 5 days, it is adding Sunday column in the front but not changing the days accordingly because it accommodates only 5 days. So, your calendar content moves 1 day over.