"Is is possible to get the actual time a document was modified before it was uploaded to a library"
Yes and no.
In many cases there will be a difference between the actual time the file was modified and when it was uploaded to SharePoint.
Quite a few file formats contain the creation and modified date in the file itself. For example, in Word click "File" | "Info" to see the actual date the Word file was created and last modified.
Which file formats use this mechanism? docx, xlsx, pptx, vsdx, pdf, jpg, dwg, audio and video files. For msg and eml you may want to use the sent date as the modified date.
File formats without dates are txt, zip, gif, ...
Basically, if the modified dates from SharePoint are good enough use them. If not, you will need to look for 3rd party tools that offer this capability.
Paul | SLIM Applications