why two patterns of time displayed?

[Song Jianping]

Hello all:
    Accidently I notice following outputs of "ls -l":
[root@Ultra /home]# ls -l
total 6
drwxr-xr-x   6 root     root         1024 Oct 14 03:50 ftp
drwxr-xr-x   5 root     root         1024 Oct 14 03:50 httpd
drwx------   5 ly       ly           1024 Oct 16 01:22 ly
drwx------   4 lyx      lyx          1024 Oct 14 22:37 lyx
drwxr-xr-x   2 root     nobody       1024 Apr 16  1999 samba
                                                  ^^^^^
drwx------   6 sjp      sjp          1024 Nov  2 16:58 sjp

why is the time pattern of "samba"(Apr 16  1999) different from the
time pattern of other directories?

Any hints?