A file can have two timestamp attributes: accessed and modified. You can set them individually, or both to the same time.
If the accessed and modified time should be the same:
$ touch -a -m -t 201512180130.09 fileName.ext
-a = accessed -m = modified -t = timestamp - use [[CC]YY]MMDDhhmm[.ss] time format
If you wish to use
NOW just drop the
-t and the timestamp.
To verify they are all the same:
See: touch man