Are Babies Ever Born on Their Due Date?

Seriously. My coworker, Charlene, went into labor yesterday. She's due on March 21st. Just a little early. So I am a little STRESSED because my work basically doubled overnight. I think that since a baby has yet to be actually born my supervisor is in complete denial and still thinks there's a chance Charlene will be able to work this event on Saturday. Hello? Can we get a clue?