It's supposed to be an efficiency measure. i.e. when you're taking a substring you won't create a new char array, but merely create a window onto the existing char array.

Is this worthwhile ? Maybe. The downside is that it causes some confusion (e.g. see this SO question), plus each String object needs to carry the offset info into the array, even if it's not used.

EDIT: This behaviour has now changed as of Java 7. See the linked answer for more info

You can use Patterns for example :

String str = "Niedersachsen,NOT IN CHARGE SINCE: 03.2009, CATEGORY";
Pattern p = Pattern.compile("\\d{2}\\.\\d{4}");
Matcher m = p.matcher(str);

if (m.find()) {
    System.out.println(m.group());
}

Output

03.2009

Note : if you want to get similar dates in all your String you can use while instead of if.

Edit

Or you can use :

String str = "Niedersachsen,NOT IN CHARGE SINCE: 03.03.2009, CATEGORY";
Pattern p = Pattern.compile("SINCE:(.*?)\\,");
Matcher m = p.matcher(str);

if (m.find()) {
    System.out.println(m.group(1).trim());
}