A legend collected in Maryland from black residents around 1925 says that Job, of the Bible, was born on February 30. When God tested Job's faith, among the suffering man's cries to heaven were these words:
Let the day perish wherein I was born, and the night in which it was said, There is a man child conceived. Let that day be darkness; let not God regard it from above, neither let the light shine upon it. Let darkness and the shadow of death stain it; let a cloud dwell upon it; let the blackness of the day terrify it. As for that night, let darkness seize upon it; let it not be joined unto the days of the year, let it not come into the number of the months. (Job 3:3-6)
And so, when God had proved to himself that Job was a faithful man and finally answered his prayers, February 30 disappeared from the calendar forever.

Source: The Folklore of American Holidays. Hennig Cohen and Tristram Potter Coffin, editors. 1st ed. Detroit : Gale Research, 1987.