Timely's first publication, Marvel Comics #1 (cover dated Oct. 1939), included the first appearance of Carl Burgos' android superhero the Human Torch, and the first appearances of Bill Everett's anti-hero Namor the Sub-Mariner, among other features. The issue was a great success, with it and a second printing the following month selling, combined, nearly 900,000 copies. While its contents came from an outside packager, Funnies, Inc., Timely had its own staff in place by the following year. The company's first true editor, writer-artist Joe Simon, teamed with artist and emerging industry notable Jack Kirby to create one of the first patriotically themed superheroes, Captain America, in Captain America Comics #1 (March 1941). It, too, proved a hit, with sales of nearly one million. Goodman formed Timely Comics, Inc., beginning with comics cover-dated April 1941 or Spring 1941.

What was the cover date on Marvel Comics #1?