Update Date Modified and Date Created in Windows Folder
Nirsoft has another great free utility that you can download at http://www.nirsoft.net/utils/bulk_file_changer.html . Bulk File Changer lets you drag and drop all of the files in a folder (or series of folders) into the program. If you hit CTRL + A
. . . then all you need to do is go to the Action menu and select 'Change Time / Attributes'
After you click 'Do it', a folder with these dates:
. . . is changed to the dates and/or times you specify.