Copying files TIMESTAMP wrong

Hi all,
The system
New install of 13.1, also installed Samba and Nettatalk. for file sharing on Windows and Macintosh network.
Added users account for both samba and MAC.

Users can connect from both with no problem.

Problem:
From a MAC mounted volume, the user copy's files from one folder to another, these files are Adobe PS and adobe PDF files.
The time stamp on both files " Before " copying is the same.
However , after copying to the needed folder, the time stamp ONLY on the Adobe PS , file changes by 6 hours.
Some PS, files go 6 hours ahead other 6 hours behind.

Please advise,
Thanks

Dave M