I have no idea how to fix this myself, but I am experiencing the same problem. It seems to be a problem only on Windows XP. We have several machines in our office and only the XP machines have this issue, while the Windows 2000 machines work just fine.
I'm going to play around with it a bit, but I have no solutions at this time.
Ok, I figured it out. I'm not sure if this is a JBoss error, or a Windows error or what.
1. Open up the Windows date/time configuration windows (double-clicking the clock is the easiest way).
2. Click on the "Time Zone" tab.
3. Verify that the "Automatically adjust clock for daylight saving changes" checkbox is checked.
If the checkbox is checked your JBoss time will be correct. Otherwise it will be one hour behind.
Hope this helps.