An old ls manual page I have says that the ls -c option lists the "time of file creation." Boo, hiss! That's an old UNIX myth. UNIX keeps three times for each file: last modification (mtime), , and last modification (ctime). A file's ctime is changed when the file is modified or when something kept in the inode (number of hard links, owner, group, etc.) has been changed. If you need to find out when that time was changed, use ls -lcr or .
Many computer sites check the ctime to decide which files to back up.