Sometimes I think that what is happening is that you are looking through a listing of msgs in one of the many sub-forums and reading the ones that you have an interest in. You do not notice the date the first msg was posted or the date of the last msg.
The first picture shows the dates two messages were started. One was in January of last year and the msg below it in August of 2005. Then at the other side is the date of the last time someone replied which was February 1 of last year. The order that the msgs are shown is based on the last reply. If someone was to reply to either on of those then the msg is moved to the top. Not sure if that give any help in figuring out how old a msg thread is.
What I usually do is click on the "New Posts" and when that opens up it gives a listing of msgs with one or more new replies. They are in order of the last reply with the most recent at the very top. I can then scroll down through the list going from page 1 to page 2 to page 3 and so on. After about 4 or 5 pages I get to msgs that already existed the last time I took a look.
Maybe that helps, maybe not.