The ctime is the change time, but this is not the same as the file's modification time (mtime). The ctime is the last time the file's status was changed. So, oftentimes this will be the date the file was added to your system. Very useful indeed!
This command will display the file's ctime in the date spot instead of the file's mtime:
ls -lc filename
This will show you the directory sorted by the ctime:
This will show you the directory sorted reverse by the ctime: