It won't let me comment directly on the incorrect messages - but let me just warn everyone, that the definition of the /XN and /XO options are REVERSED compared to what has been posted in previous messages.
The Exclude Older/Newer files option is consistent with the information displayed in RoboCopy's logging: RoboCopy will iterate through the SOURCE and then report whether each file in the SOURCE is "OLDER" or "NEWER" than the file in the destination.
Consequently, /XO will exclude OLDER SOURCE files (which is intuitive), not "older than the source" as had been claimed here.
If you want to copy only new or changed source files, but avoid replacing more recent destination files, then /XO is the correct option to use.