You should note that the datestamp will be current if you write out the file during the edit session without quitting the editor. The datestamp is only wound back when you quit the editor. You should not use ktvi if the changes will result in a change of size for a type definition, such as a C union or struct.
ktvi checks the EDITOR environment variable, and will use the editor specified, otherwise defaulting to vi.
ktvi assumes that any command-line argument starting with '+' or '-' is a switch to the editor, and not a file.