Start by running "robocopy /?" and review the help output.
If you want to copy based on file age, you have to tell robocopy how long. I don't think that you will need the /XO switch.
/MAXAGE:n :: MAXimum file AGE - exclude files older than n days/date.
/MINAGE:n :: MINimum file AGE - exclude files newer than n days/date.
Use the /l switch to test robocopy. It will just list what it will do without actually copying any files.
This command will copy files that have NOT changed in the past 2 days.
robocopy c:\temp\foo1 c:\temp\foo2 /e /mt /zb /r:1 /w:1 /copy:DATSO /minage:2 /l
This command will only copy files that have been changed in the past 2 days.
robocopy c:\temp\foo1 c:\temp\foo2 /e /mt /zb /r:1 /w:1 /copy:DATSO /maxage:2 /l
Note that robocopy will not report on the file names if they already exist in the destination folder. You can add the /v switch to have it report on all files.