A controlled document has one current version. Replacing it keeps the history and moves the current version forward. The calendar is the same library, drawn by review date.
Versions
The register shows the current version. Replace the document when a new version should become current. Version history stays with the document, including on a generated policy, so the register and the document tell the same story.
The document calendar
Open Document Calendar. Red is a next review that is overdue. Orange is a next review due within 30 days. Green is a next review later than that. Yellow is last reviewed. Purple is when the document was created. Open an event to go to that document.