5.5.2.3. Tracking of File Creation, Access, Modification Times
Most file systems keep track of the time at which a file was created; some also track modification and access times. Over and above the convenience of being able to determine when a given file was created, accessed, or modified, these dates are vital for the proper operation of incremental backups.
More information on how backups make use of these file system features can be found in Section 8.2, “Backups”.
