Gaye, the times shown in the forum are for the time zone where the computer is located - that is, the server where the Web site is running. This happens to be in Dallas, which is 16 hours behind us at the moment. (Being in Melbourne, I'm in the same time zone as you.)
You can set things up so the times in the forum are translated to your own time zone - click the Profile tab and then click on "Look and Layout Preferences" under the "Modify Profile" heading on the left hand side of the screen. Then you should see a field labelled "Time Offset", where you can enter 16, and then click the "Change Profile" button towards the bottom of the screen. The only drawback to this is that you have to adjust the offset by an hour or two every so often because someone has started or stopped daylight savings.
As for the reason the server is in Dallas, I buy my Web hosting services through an Australian business, but the best value packages are usually hosted in the US for some reason. Apart from time zones, it doesn't make any real difference where it is.
(The reason the puzzles use GMT is just because that seemed like a reasonably neutral time zone to use.)