Change date format info for "W"

The "W" format is the ISO-8601 week number, which can be 53.

Therefore, the range was changed to "1..53".

If you want to check this quickly, run the command:

```
php -r "echo date('W',  1104537600 );"
```
=> 53.

(1104537600 is the timestamp for 2005/01/01)