There are differences between the timestamps in UNIX :
Three times tracked for each file in Unix are these:
access time – atime
change time – ctime
modify time – mtime
atime – File Access Time
Access time shows the last time the data from a file was accessed – read by one of the Unix processes directly or through commands and scripts.
ctime – File Change Time
ctime also changes when you change file's ownership or access permissions. It will also naturally highlight the last time file had its contents updated.
mtime – File Modify Time
Last modification time shows time of the last change to file's contents. It does not change with owner or permission changes, and is therefore used for tracking the actual changes to data of the file itself.
So if you use ctime you will search the files where theirs datas or their owners/permissions has not been modified since 5 days.
To be sure of the dates of yours files, you can see the differents timestamps with the following command :
# stat fi.le
Access : 2016-11-14 11:36:21.850314996 +0100
Modif. : 2016-11-10 14:20:25.378246071 +0100
Changt : 2017-02-08 15:00:57.464000000 +0100
For example, I change the owner of fi.le
today, so the ctime is today and the mtime is stayed in 2016.
And after cat fi.le, the access time is also updated :
# cat fi.le
# stat fi.le
Accès : 2017-02-08 15:03:09.400000000 +0100
Modif. : 2016-11-10 14:20:25.378246071 +0100
Changt : 2017-02-08 15:00:57.464000000 +0100