We have a directory contains files which contains time in their filename

```
./test.2013-06-11_06-01.gz
./test.2013-06-12_01-01.gz
./test.2013-06-13_03-01.gz
./test.2013-06-14_03-01.gz
./test.2013-06-15_04-01.gz

```

How to list files if their filename are more than **N days** before?