Being born on this day gives the illusion that a person ages slower. When the rest of us turn 40, a leap day baby will have only had 10 birthdays. So, when Julie Schwartz was asked for Superman’s birthday in his “Answer Man” column, he cleverly replied that Superman celebrates his birthday on February 29th, which is why is so young. Turns out, Krypton’s calendar is not the same as the one on Earth and 18 Krypton years are equal to 25 of those on Earth. So, this was just an approximate date based on the equivalent Kryptonian date. So, Happy Birthday to the Man of Steel!
For example, in 1950, long before Schwartz’s announcement of February 29th date, ACTION COMICS #149 announced that the Golden Age Man of Steel was born on Kryptonopolis was in October.
The February 29th date is again given in one of the best Superman stories ever written, Alan Moore tell us what to get “For the Man Who has Everything” in SUPERMAN ANNUAL #11 in 1985. This was also adapted in a great JLU cartoon episode.