I know how to modify file's creation date, but in Excel (xlsx) in file statistics/attributes/properties/whatever it still has the original creation date/last printed date etc. I was wondering if there is any way to modify this data.
The created dates, etc., are from the filesystem (I think the printed date is stored in the file) so any utility that can modify those dates for any file should be able to do it for your spreadsheet file. Here is an article that lists a few of those utilities.
I figured it out, and I guess it might be useful for some, so Ill answer my question myself. Note this works only for the new Excel file format (xlsx) or other new MS Office formats, ie office 2007 and newer. For older file formats do like Dennis Williamson suggested bellow.
Here are basic steps:
Open the Excel file using a zip utility such as 7zip Go to folder named 'docProps' Extract the file name 'core.xml' Open the file using a plain-text editor such as Notepad or Notepad++
You will see most(all?) file atributes inside angle bracket tags, such as
Modify the date or other info that goes BETWEEN the tags ie the date above. WARNING! don't modify the stuff INSIDE the tags (angle brackets) unless you know what are you doing.
Save the file when done. Go back into the zip utility and change the original 'core.xml' with the one you just edited. If using 7zip its as simple as drag and dropping it back and confirming overwrite. Go inside excel and confirm that all the information is modified. The end.
Using 7Zip as described above works well. Just be aware that time is stored as UTC (aka GMT) and you will need to adjust it to your time zone.
If for some reason you want to cover your tracks, editing the core.xml file will show that the file was modified on the date you made the modification. In that case, you should use Plan B, described in the next paragraph.
Saving to a new file won't work, at least not in Excel 2010; it carries the original creation date along with everything else into the new file. However, moving all of your worksheets to a new workbook gives you a clean start datewise...the date created will be the date you moved the worksheets.