Since his debut nearly 78 years ago, Superman has had a handful of different "birth dates," including Dec. 1 and sometime in October, but Feb. 29 -- Leap Day! -- is the one that's more or less stuck. It's the date longtime Superman editor Julius Schwartz settled on, and the one mentioned both in the celebrated 1985 story "For the Man Who Has Everything" and in Time's 1988 cover story.

And it's the date DC Comics has embraced (although not always consistently in its books), and is celebrating this year with a 65 percent-off sale on select Superman digital collected editions.

Why Feb. 29 and not, say, April, when Action Comics #1 debuted, or June, when Clark Kent celebrates his birthday? Apparently to slow the (surprisingly vain) Man of Steel's aging process: See, he only has a birthday every four years. Eh, I'd do that too, if I could get away with it.

So, to the Man Who Has Everything: Happy birthday! We'll get together again in 2020.