Here are some questions related to the timestamp of the files inside Harvest.
The repository currently shows the Last Updated field on every screen. The value of this Last Updated field is derived from the last modified time of the file on disk.
Release : 14.0 and up
Each version of a file has an updated date equivalent to the time the file was checked out (for "R" tag files) or the time it was checked in (for "N" tag files). When you check out a file, a new version is created, and it's a placeholder only. It doesn't have content behind it until the new version of the file is checked in. The timestamp you're expecting to see is likely the check-in time of the previous version.
During the creation of Project B from Project A the timestamp that shows when the version was checked in is in the "File Modified On" column. You can find this column by looking in the Lists tab and scrolling all the way to the right. It will show the timestamp of the file that was checked in. This works whether you have selected a folder in the data view or the "Versions" node under a package.
This column is not available in the "Find Versions" tool, but the Lists tab does provide this information.