bufferedwriter or windows, which one of you is my enemy?

I was planning to name a file I generated using the username and the date of generation, so my naming format was like "01-03-2010-13:33-user1". When I'm trying to do that with BufferedWriter of our beloved Java, this file is not created. ":" is not allowed by Windows so a file with "01-03-2010-13" as a name is created and nothing is inserted although I called bufferedWriter.write("something"). The good part is that no exception is thrown by BufferedWriter. Great isnt it?