The on-sale date is the publication date reported in the U. S. Copyright Office filing.
Cover colors credit from Greg Theakston, via the GCD Error List (2008-4-5).
First appearance of TNT & Dan (appears next in World's Finest Comics #5). Order of TNT appearances determined by copyright dates (Star Spangled #7 on Feb 1st 1942, World's Finest #5 on Feb 3rd 1942). Note that the two books essentially debuted at the same time.