Having trouble with Pattern Matching

Not sure where this is supposed to go.
I have been having problems working out how to pattern match dates from some headers.

I have been getting the body of a webpage and extracting the links so I get some urls which I am then going to use to get a head request for each. Then I am going to take the part of the head request that says when the webpage was last updated and return that. Problem is I am pretty sure the following pattern match on dates like the following [Last-Modified: Sun, 04 Nov 2012 20:59:59 GMT] is horribly wrong.

Code:

---

Pattern pdate = Pattern.compile("Last-Modified:(.*?)GMT");
Matcher mdate = p.matcher(information);
                       
                        ArrayList<String> Dates = new ArrayList<String>();

                        while (mdate.find()) {
                                String dates = mdate.group(1).toString();
                                Dates.add(dates);
                                System.out.println(m.group(1));
                        }

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Can anyone give me a better pattern match / correct my code? I would also be incredibly grateful if you would point out any potential problems that you spot.

Well, according to my regex viewer, it does work. Perhaps the problem isn't in the regex itself, but maybe your input?

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