If you put “the” in the “Search Forum” box and hit the Return key, the “Forum Search Results” page will appear. On top of the page there are numbers that begin with 1 and end with 67. If you click the number 67, you can go to page 67. At the bottom of the page you can see the oldest thread “Play lists keep disappearing”.
If you open the thread, you will find that the thread was created on May 07, 2015. The last or latest message was posted on June 10, 2015.
If you go back to the “Forum Search Result” page and choose “Last year” instead of “All time”, you will find that the oldest thread was created on June 05, 2015.
If you choose “Open Forum in English” instead of “All Forums”, other things being equal, the oldest thread was created on September 8, 2014.
If you choose “Open Forum in English” and “All time”, you will find the same result, that is, September 8, 2014. You will probably conclude that “All time” means “Last year” in the “Search Forum” function on the LingQ site and that “Last year” began last September.