The publish dates of song lessons can be found by using the "Newest" sort in the "Songs" section of GT. Unfortunately, that's the only place I know of that gives the publish date. I say unfortunately because the only way I know how to find the publish date from there is to scroll through the individual pages until I find the song I'm looking for.

For example, if I want to find the lesson publish date of Surfer Girl I have to scroll through (currently) 28 pages of lesson listings until I hit upon that title because that sort is in chronological order, newest to oldest. Clicking on a genre will shorten the listing but still yields a newest to oldest list which can be quite lengthy if it's something else than Surf.

There should be an easier more direct look up for publish dates. Is there?