[vasile@tuzik ~]$ mkdir testdir
[vasile@tuzik ~]$ cd testdir/
[vasile@tuzik testdir]$ mkdir 2007_05_9 2007_03_91 2005_05_9
[vasile@tuzik testdir]$ cat mvdir.sh 
#!/bin/sh
dir=$(echo "$1"|tr _ / )
mkdir -p "$dir"
rmdir "$dir"
mv "$1" "$dir"
[vasile@tuzik testdir]$ find -type d -name '????_*_*' -exec sh ./mvdir.sh \{\} \;
find: ./2005_05_9: No such file or directory
find: ./2007_05_9: No such file or directory
find: ./2007_03_91: No such file or directory
[vasile@tuzik testdir]$ ls -l *
-rw-rw-r-- 1 vasile vasile   79 2007-12-28 17:40 mvdir.sh

2005:
total 8
drwxrwxr-x 3 vasile vasile 4096 2007-12-28 17:41 05

2007:
total 16
drwxrwxr-x 3 vasile vasile 4096 2007-12-28 17:41 03
drwxrwxr-x 3 vasile vasile 4096 2007-12-28 17:41 05
[vasile@tuzik testdir]$ ls -l */*
2005/05:
total 8
drwxrwxr-x 2 vasile vasile 4096 2007-12-28 17:41 9

2007/03:
total 8
drwxrwxr-x 2 vasile vasile 4096 2007-12-28 17:41 91

2007/05:
total 8
drwxrwxr-x 2 vasile vasile 4096 2007-12-28 17:41 9
[vasile@tuzik testdir]$