Superman has had a few different birthdates over the years, but perhaps his most well-known day of birth is today, February 29, aka Leap Day.
But while it is Superman's birthday, it is not, however, Clark Kent's birthday. Clark's birthday is celebrated on June 18, the date on which the Kent family first discovered the young Kryptonian in Kansas. Or it usually is, at least. And Leap Day isn't Superman's publication birthday either. That's in June, when the first issue of Action Comics featuring the character was released.
So why exactly is Superman's birthday Feb. 29? For a Kryptonian who never seems to age, having a birthday once every four years makes more sense than any other random date I suppose. Superman might as well be Leap Day Williams.
As you might guess, it's a little unclear exactly how old Superman the character is. In the 1990s the Man of Steel was described as being around 34 or 35 years old, while earlier comics made references that seemed to indicate Superman to be closer to the age of 29.
Not that any of that really matters. After all, he's both Superman and a comic book character. Not only do comic characters cheat death over and over again, but very often their ages remain nearly fixed in time, despite characters like Batman having existed for decades. There is also the "fact" of Superman being near immortal to consider. In that light, it makes sense why Superman never appears to age. Though certain alternate reality stories will occasionally show other DC heroes as older, particularly the non-superpowered Batman, you'll never see a Superman with a hunchback and grey hair.
That's probably for the best. Superman is just that; a Super Man. He's supposed to be the ideal person for the world to look up to, a man that is humanity at its best and brightest potential. Getting older kind of puts a damper on all of that.
Long story short: Happy birthday Superman! We didn't get you anything, but we'll be sure to show up to your next birthday party four years from now.