Don’t forget it’s daylight savings time. You spring forward, then you fall back. It’s like Robert Downey Jr. getting out of bed.

Letterman’s joke hinges on the familiar mnemonic for daylight saving time—“spring forward, fall back”—and then twists it into a celebrity gag. By likening the clock change to Robert Downey Jr. “getting out of bed,” the line plays on the actor’s well-publicized struggles with addiction and relapse in the late 1990s and early 2000s, implying a cycle of progress followed by setback. The humor comes from the abrupt shift from a harmless public-service reminder to a pointed, tabloid-aware punchline, a hallmark of late-night monologue comedy that relies on shared cultural knowledge and surprise misdirection.