Improving keeping track of file modification time

Among the metadata associated with a file, all modern operating systems store the last modification time, that is automatically updated to the current time whenever a program modifies the file, but can also be set directly to any desired value. When copying a file, it is debatable whether the last modification time of the copy should be set to the time of the copy operation or to the modification time of the original file, each strategy raising some serious problems. This paper proposes and analyzes a clean solution to these problems, based on separating two modification times, one associated with the file itself and another one associated with its content.