I've seen this on Surface Books and Surface Pros. It appears to be related to high resolution display settings. If the user opens Notes in Basic mode (runs nlnotes.exe instead of notes.exe or runs notes.exe with -basic switch), they can see their calendar as before. Similarly, if they set the Surface Book to a lower resolution, and relaunch Notes, they can see when they are booked in the One Day or One Week view. Reinstalling the video driver sometimes addresses the problem.
Renaming the data\workspace folder has had no effect on the problem.