Please see attached: everything is off by one day for this one user. We don't know how to fix it. (If you look, the days along the top are off. Instead of going Sunday to Saturday, it looks to be going Saturday to Friday. )
I don't have this issue, and when I log in as her, I don't see it there either.
Check to see if the Zoom setting on the user's computer is set to something other than 100%. If not at 100%, change it to 100% and the calendar should render correctly. This issue came up for us last year, and that was what was causing the calendar issue.