I had a bunch of .mp4 and .3gpp video files whose file "create" and "last modified" filesystem dates did not match the meta data inside of the file, and this was causing problems because many apps use the filesystem dates when sorting video files (rather than using the metadata inside the video files).
I found ExifTool could fix this. Using the ExifToolGUI I could fix them one at a time. By using the ExifTool cmd-line tool I was able to change them all at once. The biggest challenge was that most of the documentation was on how to modify the internal meta data, but I wanted to "copy" from the meta data to the filesystem timestamps.
The first trick is to figure out what the "tags" are for the internal metadata and the file system. I found the ExifTool FAQ #24 which shows how to query for the times:
> exiftool -time:all -a -G0:1 -s MyVideo.mp4
[File:System] FileModifyDate : 2014:09:07 19:35:32-06:00
[File:System] FileAccessDate : 2015:10:24 22:55:22-06:00
[File:System] FileCreateDate : 2015:10:24 22:55:22-06:00
[QuickTime] CreateDate : 2013:09:14 00:52:38
[QuickTime] ModifyDate : 2013:09:14 00:52:38
From the above the CreateDate & ModifyDate are the internal meta data, and the FileModifyDate etc are the filesystem.
So to update the filesystem date to match the metadata CreateDate I used this command:
> exiftool "-CreateDate>FileModifyDate" MyVideo.mp4
To modify multiple files I used wild-cards on the filename, like *.mp4 to update all mp4 files in the current directory.
Related, to update the file system time for image files to match the meta data:
> exiftool "-DateTimeOriginal>FileModifyDate" MyPicture.jpg
Note that most apps know how to look into image metadata, so setting the filesystem dates is not as important as for video files.