How to Change the File Modified Date
As you probably know, all files on your system have a "Date Modified" attached to them that can be seen by right-clicking on the file and selecting "Properties." There may be circumstances in which you would like to modify this date to a different one. But there is no way in "Properties" to do it. Fortunately, there is a freeware program called FIleDate Changer that can do this for you.
Go to NirSoft, download the FileDate Changer, and install it on your system.
Open FileDate Changer. Click on the "Add" button to browse to and select files on which you want to change the date.
Select "File Modified" from the types offered. Then type in the date to which you want the file changed, and click on "Change Files Date."