that shouldn't be.
go to your profile, and in your preferences make sure that the time zone is correct for you.
click on 'auto detect' and it will detect your time zone. Make sure you then click on SAVE. Everything should be in reference to your own time zone, this applies to everyone.
Both the threads and the post can be controlled by the user and can sometimes be rearranged by an accidental click in the wrong place.
For the threads.....go to the page showing the list of threads for the Discussion Forum. Just above the pink posts at the top of the list is a blue banner with the titles "Subject/Started By", "Replies/Views" and "Last Post". To show the newest posts at the top of the page, click on the words Last Post and make sure there is a triangle pointing down next to it. If it is pointing up, click on last post again and it will flip.
For the display of the posts inside a thread, this is also customizable as some people like them to be in different orders. If you want the newest posts at the top of a thread so you don't have to scroll through all the old stuff, click on the Profile tab at the top of the page. Then under Modify Profile, click on "Modify Layout". Here you can do a lot of stuff, but the order of the posts is controled by the check box second from the bottom. Check it to have the most recent posts at the top and leave it blank to have the most recent posts at the bottom. Remember this is for the posts or comments within a thread only.
While you are in the Profile, on the same page, check to see if your Time is correct on the section at the top called Time Offset. Click on the blue auto detect to set your GMT off set. Below is the display of the current time which for some reason today shows UTC and I have no idea why. I don't think that this is the source of your problem. This is used to display the time of each post so it may look like people are posting at odd hours. The order of each post/thread should be relative to each other.