SharePoint Online should preserveve modified date and more from imported files
When importing files from file shares to SharePoint in Office 365 the modified date and so on is set equal to the import time. This means SharePoint is not able to display the correct historic dates of files, though it actually keep initially modified date when viewing file details in Explorer view so the date actually still is there but not visible.
For SharePoint to be a true content management system basic metadata should be preserved when moved to SharePoint. Not being able to track such metadata may for many companies be an issue and at the same time end users will think old historic files are actually quite new.
Paul de Jong | SLIM Applications commented
Several of the tools provide this functionality.