Firefox does not have a time zone by itself. Can you be more specific about what problem you are seeing? Is it a specific website you are visiting? Are you using a time-related add-on? Also go ahead and check that your Windows installation has the correct time zone set. To find out how to do this, take a look at [http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/windows_date_change_time.mspx?mfr=true this Microsoft article].