Only good girls keep diaries. Bad girls don’t have time.

A characteristically wry Tallulah Bankhead quip, the line plays on the moralizing stereotype of the “good girl” as orderly, self-monitoring, and domesticated—someone who records her days for propriety or self-improvement. The punchline flips the expectation: the “bad girl” is not merely rebellious but too busy living (and perhaps courting scandal) to pause and document it. The joke also hints at performance and reputation: diaries preserve evidence, while a life lived impulsively leaves fewer written traces. As with much of Bankhead’s persona, the humor depends on theatrical exaggeration and a knowing challenge to conventional female respectability.