Yes, it was established in a 1967 comic that Superman's birthday (not Clark Kent's) was to be celebrated on February 29, Leap Day. Here's an article about it.
Today's page-by-pages from October, 1963's Action Comics #305 Come just past the staple -- we're halfway through!
And who would want a bunch of old stamps, anyway, where there were bubble-gum monster cards to be had, and marbles to be played?
See you on Wednesday, when we'll start the second story in this issue, "The Girl Who Hated Supergirl!"