Harvest Software Change Manager v12.x and higher
There is a feature in Workbench that allows you to change the package name by selecting and then clicking again on it.
Here is a package name after clicking just once to highlight it:
If I click again on the package name after selecting it, the package name goes into Edit mode
The difference is subtle unless you're looking for it, but you will see the background color shrinks to just the height of the letters, and a flashing cursor appears at the end of the package name.
Whether you actually change the name or not, when you click away from the package to something else on the window, an UPDATE_PACKAGE transaction gets triggered in Harvest, thus changing the Modified Date. You won't see the date change for the duration of your current Workbench session because the data is cached locally, but if you close Workbench and reopen, the package now has a new Modified Date and Time.
So the Modified Date is changing when your user inadvertently puts the package name into Edit mode.
But, this can be prevented. In Administrator Tool if you navigate to the project and state your package is in, and right click on the Package name and select "Properties" and the "Access" tab, there are 2 access lists associated with states. The "Update" access list controls which users have permission to update the properties of the state (name, list of processes, etc). The "Update Package" access list controls which users have permission to update the properties of any packages in that state - including the package name. If you remove user groups from the "Update Package" access list, then they can click on the package name all they want and it will never go into edit mode, thus preventing the UPDATE_PACKAGE transaction and the change in the Modified Date.
To read more about access permissions, and which types of access control which actions, read the "Control Object Access" chapter of the online documentation.