PROBLEM: After backup, all ZIP files have file date/time changed

I have had Acronis True Image Home 2011 for a couple of months, three instances backing up 3 new PCs with Windows 7 opsys. All three machines have the same backup scheme: Full backup followed by three incremental backups. Works fine except for the fact that the date/time of all ZIP files that get backed up (and I have a lot of them) are changed to the current date/time. This REALLLLY sucks. I can't imagine why the Acronis software would need to do this. And besides, it is really unacceptable to _change_ the files that are being backed up. I have been a data processing professional for twenty plus years, and my long-standing philosophy and tradition is that ZIP files should have a file date stamp equal to the date stamp of the _latest_ file, at least for those ZIP that I have created to backup source code, work-in-progress, etc.

Please tell me that this is a known issue, or that there are workarounds, or that there is a damn good reason for a backup program to _change_ the files being backed up.