Modification dates on Windows server changed?

I have a ton of files on a Windows DFS server that suddenly got the wrong modification dates. I don't think the files have been restored (there's 30,000 affected files) and all the dates reverted to a date in 2005 that the files were first copied to the DFS drive.

In a Windows PC the file and folder dates are all correct. How can I correct the NFS modification date to restore this capability?

Thanks
Darryl Zurn

G5 Mac OS X (10.4.6)