Both the original Captain Marvel and Superman celebrate birthdays on Leap Day, February 29th. Captain Marvel was, of course, not born in the conventional sense, but chose that day for celebration to mock Dr. Sivana who had wanted to make that day his rival’s “deathday."
Kal-El was born on 38 Eorx 9998, by Kryptonian reckoning, a date not easily translatable any Earth calendar. His friends in the Justice Society, and later the Justice League, chose those Leap day to celebrate it.
Superman would have one of his most memorable birthdays on that day in 1984, when Mongul exposed him to the alien plant called the Black Mercy. He had to be rescued by his friends from the Justice League, particularly the quick thinking of Robin, Jason Todd.