What does a man do only once in his lifetime, but women do once a year after they are 29?
This sounds like a riddle, and the answer to this particular riddle is usually: "Celebrate their 30th birthday." The joke suggests that a man turns 30 only once, while a woman, humorously, keeps turning 29 each year, never admitting to being older than 29. It leans on the stereotype and humorous concept that some women prefer to avoid disclosing their true age or dislike the idea of turning 30 due to societal pressures about youth and beauty.
Of course, in reality, both men and women age at the same rate, and everyone has each birthday only once. This riddle plays on social norms and stereotypes for comedic effect.